Add ability to select distance unit

lib/app.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/services/api_service.dart';
 import 'package:mileograph_flutter/services/authservice.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:mileograph_flutter/services/endpoint_service.dart';
 import 'package:mileograph_flutter/ui/app_shell.dart';
 import 'package:provider/provider.dart';
@@ -16,6 +17,9 @@ class App extends StatelessWidget {
         ChangeNotifierProvider<EndpointService>(
           create: (_) => EndpointService(),
         ),
+        ChangeNotifierProvider<DistanceUnitService>(
+          create: (_) => DistanceUnitService(),
+        ),
         ProxyProvider<EndpointService, ApiService>(
           update: (_, endpoint, api) {
             final service = api ?? ApiService(baseUrl: endpoint.baseUrl);

lib/components/calculator/route_summary_widget.dart

@@ -1,4 +1,6 @@
 import 'package:flutter/material.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
+import 'package:provider/provider.dart';
 
 class RouteSummaryWidget extends StatelessWidget {
   final double distance;
@@ -12,13 +14,14 @@ class RouteSummaryWidget extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final distanceUnits = context.watch<DistanceUnitService>();
     return Padding(
       padding: const EdgeInsets.all(16),
       child: Row(
         children: [
           Expanded(
             child: Text(
-              "Total Distance: ${distance.toStringAsFixed(2)} mi",
+              "Total Distance: ${distanceUnits.format(distance, decimals: 2)}",
               style: Theme.of(context).textTheme.titleMedium,
             ),
           ),
@@ -48,6 +51,7 @@ class RouteDetailsView extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final distanceUnits = context.watch<DistanceUnitService>();
     final highlightColor = Theme.of(context).colorScheme.primary;
     final mutedColor = Theme.of(context).colorScheme.outlineVariant;
     return Column(
@@ -78,7 +82,9 @@ class RouteDetailsView extends StatelessWidget {
                       ? TextStyle(color: highlightColor, fontWeight: FontWeight.w600)
                       : null,
                 ),
-                trailing: Text("${costs[index].toStringAsFixed(2)} mi"),
+                trailing: Text(
+                  distanceUnits.format(costs[index], decimals: 2),
+                ),
               );
             },
           ),

lib/components/dashboard/leaderboard_panel.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 
 import 'package:provider/provider.dart';
 
@@ -9,6 +10,7 @@ class LeaderboardPanel extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final data = context.watch<DataService>();
+    final distanceUnits = context.watch<DistanceUnitService>();
     final leaderboard = data.homepageStats?.leaderboard ?? [];
     final textTheme = Theme.of(context).textTheme;
     if (data.isHomepageLoading && leaderboard.isEmpty) {
@@ -82,7 +84,10 @@ class LeaderboardPanel extends StatelessWidget {
                         ),
                       ),
                       trailing: Text(
-                        '${leaderboard[index].mileage.toStringAsFixed(1)} mi',
+                        distanceUnits.format(
+                          leaderboard[index].mileage,
+                          decimals: 1,
+                        ),
                         style: textTheme.labelLarge?.copyWith(
                           fontWeight: FontWeight.w700,
                         ),

lib/components/dashboard/top_traction_panel.dart

@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
-
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 
 class TopTractionPanel extends StatelessWidget {
@@ -9,6 +9,7 @@ class TopTractionPanel extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final data = context.watch<DataService>();
+    final distanceUnits = context.watch<DistanceUnitService>();
     final stats = data.homepageStats;
     final locos = stats?.topLocos ?? [];
     final textTheme = Theme.of(context).textTheme;
@@ -76,9 +77,12 @@ class TopTractionPanel extends StatelessWidget {
                               style: textTheme.bodySmall?.copyWith(
                                 fontStyle: FontStyle.italic,
                               ),
-                            ),
+                      ),
                       trailing: Text(
-                        '${locos[index].mileage?.toStringAsFixed(1)} mi',
+                        distanceUnits.format(
+                          locos[index].mileage ?? 0,
+                          decimals: 1,
+                        ),
                         style: textTheme.labelLarge?.copyWith(
                           fontWeight: FontWeight.w700,
                         ),

lib/components/legs/leg_card.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 
 class LegCard extends StatefulWidget {
@@ -26,6 +27,7 @@ class _LegCardState extends State<LegCard> {
   @override
   Widget build(BuildContext context) {
     final leg = widget.leg;
+    final distanceUnits = context.watch<DistanceUnitService>();
     final routeSegments = _parseRouteSegments(leg.route);
     final textTheme = Theme.of(context).textTheme;
     return Card(
@@ -181,7 +183,7 @@ class _LegCardState extends State<LegCard> {
               crossAxisAlignment: CrossAxisAlignment.end,
               children: [
                 Text(
-                  '${leg.mileage.toStringAsFixed(1)} mi',
+                  distanceUnits.format(leg.mileage, decimals: 1),
                   style: textTheme.labelLarge?.copyWith(
                     fontWeight: FontWeight.w700,
                   ),

lib/components/pages/dashboard.dart

@@ -7,6 +7,7 @@ import 'package:mileograph_flutter/components/dashboard/top_traction_panel.dart'
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/authservice.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 
 class Dashboard extends StatefulWidget {
@@ -23,6 +24,7 @@ class _DashboardState extends State<Dashboard> {
   Widget build(BuildContext context) {
     final data = context.watch<DataService>();
     final auth = context.watch<AuthService>();
+    final distanceUnits = context.watch<DistanceUnitService>();
     final stats = data.homepageStats;
 
     final isInitialLoading = data.isHomepageLoading || stats == null;
@@ -46,9 +48,15 @@ class _DashboardState extends State<Dashboard> {
               ListView(
                 padding: const EdgeInsets.all(16),
                 children: [
-                  _buildHero(context, auth, data, stats),
+                  _buildHero(context, auth, data, stats, distanceUnits),
                   const SizedBox(height: spacing),
-                  _buildTiles(context, data, maxWidth, spacing),
+                  _buildTiles(
+                    context,
+                    data,
+                    distanceUnits,
+                    maxWidth,
+                    spacing,
+                  ),
                 ],
               ),
               if (isInitialLoading)
@@ -81,6 +89,7 @@ class _DashboardState extends State<Dashboard> {
     AuthService auth,
     DataService data,
     HomepageStats? stats,
+    DistanceUnitService distanceUnits,
   ) {
     final colorScheme = Theme.of(context).colorScheme;
     final greetingName =
@@ -119,14 +128,14 @@ class _DashboardState extends State<Dashboard> {
                 _metricTile(
                   context,
                   label: 'Total mileage',
-                  value: '${totalMileage.toStringAsFixed(1)} mi',
+                  value: distanceUnits.format(totalMileage, decimals: 1),
                   icon: Icons.route,
                   color: colorScheme.onPrimaryContainer,
                 ),
                 _metricTile(
                   context,
                   label: 'This year',
-                  value: '${currentYearMileage.toStringAsFixed(1)} mi',
+                  value: distanceUnits.format(currentYearMileage, decimals: 1),
                   icon: Icons.calendar_today,
                   color: colorScheme.onPrimaryContainer,
                 ),
@@ -215,6 +224,7 @@ class _DashboardState extends State<Dashboard> {
   Widget _buildTiles(
     BuildContext context,
     DataService data,
+    DistanceUnitService distanceUnits,
     double maxWidth,
     double spacing,
   ) {
@@ -229,9 +239,9 @@ class _DashboardState extends State<Dashboard> {
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.stretch,
               children: [
-                _buildOnThisDayCard(context, data),
+                _buildOnThisDayCard(context, data, distanceUnits),
                 const SizedBox(height: 16),
-                _buildTripsCard(context, data),
+                _buildTripsCard(context, data, distanceUnits),
                 const SizedBox(height: 16),
                 const LatestLocoChangesPanel(expanded: true),
               ],
@@ -256,13 +266,13 @@ class _DashboardState extends State<Dashboard> {
     return Column(
       crossAxisAlignment: CrossAxisAlignment.stretch,
       children: [
-        _buildOnThisDayCard(context, data),
+        _buildOnThisDayCard(context, data, distanceUnits),
         const SizedBox(height: 16),
         const TopTractionPanel(),
         const SizedBox(height: 16),
         const LeaderboardPanel(),
         const SizedBox(height: 16),
-        _buildTripsCard(context, data),
+        _buildTripsCard(context, data, distanceUnits),
         const SizedBox(height: 16),
         const LatestLocoChangesPanel(),
       ],
@@ -296,7 +306,8 @@ class _DashboardState extends State<Dashboard> {
     );
   }
 
-  Widget _buildOnThisDayCard(BuildContext context, DataService data) {
+  Widget _buildOnThisDayCard(
+      BuildContext context, DataService data, DistanceUnitService distanceUnits) {
     final filtered = data.onThisDay
         .where((leg) => leg.beginTime.year != DateTime.now().year)
         .toList();
@@ -329,7 +340,7 @@ class _DashboardState extends State<Dashboard> {
           : Column(
               children: [
                 for (int idx = 0; idx < visible.length; idx++) ...[
-                  _otdRow(context, visible[idx], textTheme),
+                  _otdRow(context, visible[idx], textTheme, distanceUnits),
                   if (idx != visible.length - 1) const Divider(height: 12),
                 ],
               ],
@@ -337,7 +348,8 @@ class _DashboardState extends State<Dashboard> {
     );
   }
 
-  Widget _otdRow(BuildContext context, Leg leg, TextTheme textTheme) {
+  Widget _otdRow(BuildContext context, Leg leg, TextTheme textTheme,
+      DistanceUnitService distanceUnits) {
     final traction = leg.locos;
     return Row(
       crossAxisAlignment: CrossAxisAlignment.center,
@@ -443,7 +455,7 @@ class _DashboardState extends State<Dashboard> {
           crossAxisAlignment: CrossAxisAlignment.end,
           children: [
             Text(
-              '${leg.mileage.toStringAsFixed(1)} mi',
+              distanceUnits.format(leg.mileage, decimals: 1),
               style: textTheme.labelLarge?.copyWith(
                 fontWeight: FontWeight.w800,
               ),
@@ -498,7 +510,8 @@ class _DashboardState extends State<Dashboard> {
     );
   }
 
-  Widget _buildTripsCard(BuildContext context, DataService data) {
+  Widget _buildTripsCard(
+      BuildContext context, DataService data, DistanceUnitService distanceUnits) {
     final tripsUnsorted = data.trips;
     List trips = [];
     if (tripsUnsorted.isNotEmpty) {
@@ -543,7 +556,7 @@ class _DashboardState extends State<Dashboard> {
                                   ?.copyWith(fontWeight: FontWeight.w700),
                             ),
                             Text(
-                              '${trip.tripMileage.toStringAsFixed(1)} mi',
+                              distanceUnits.format(trip.tripMileage, decimals: 1),
                               style: Theme.of(context).textTheme.labelMedium,
                             ),
                           ],

lib/components/pages/legs.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/components/legs/leg_card.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 
 class LegsPage extends StatefulWidget {
@@ -90,6 +91,7 @@ class _LegsPageState extends State<LegsPage> {
   @override
   Widget build(BuildContext context) {
     final data = context.watch<DataService>();
+    final distanceUnits = context.watch<DistanceUnitService>();
     final legs = data.legs;
     final pageMileage = _pageMileage(legs);
 
@@ -121,7 +123,7 @@ class _LegsPageState extends State<LegsPage> {
                     children: [
                       Text('Page mileage',
                           style: Theme.of(context).textTheme.labelSmall),
-                      Text('${pageMileage.toStringAsFixed(1)} mi',
+                      Text(distanceUnits.format(pageMileage, decimals: 1),
                           style: Theme.of(context)
                               .textTheme
                               .titleMedium
@@ -212,7 +214,7 @@ class _LegsPageState extends State<LegsPage> {
           else
             Column(
               children: [
-                ..._buildLegsWithDividers(context, legs),
+                ..._buildLegsWithDividers(context, legs, distanceUnits),
                 const SizedBox(height: 8),
                 if (data.legsHasMore || data.isLegsLoading)
                   Align(
@@ -239,7 +241,11 @@ class _LegsPageState extends State<LegsPage> {
     );
   }
 
-  List<Widget> _buildLegsWithDividers(BuildContext context, List<Leg> legs) {
+  List<Widget> _buildLegsWithDividers(
+    BuildContext context,
+    List<Leg> legs,
+    DistanceUnitService distanceUnits,
+  ) {
     final widgets = <Widget>[];
     String? currentDate;
     double dayMileage = 0;
@@ -261,10 +267,8 @@ class _LegsPageState extends State<LegsPage> {
                       ),
                 ),
               ),
-              Text(
+              Text(distanceUnits.format(dayMileage, decimals: 1),
-                '${dayMileage.toStringAsFixed(1)} mi',
+                  style: Theme.of(context).textTheme.labelMedium),
-                style: Theme.of(context).textTheme.labelMedium,
-              ),
             ],
           ),
         ),

lib/components/pages/new_entry/new_entry.dart

@@ -11,6 +11,7 @@ import 'package:mileograph_flutter/components/pages/traction.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/api_service.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:mileograph_flutter/services/navigation_guard.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';

lib/components/pages/new_entry/new_entry_draft_logic.dart

@@ -235,6 +235,7 @@ extension _NewEntryDraftLogic on _NewEntryPageState {
     required String id,
     bool includeTimestamp = true,
   }) {
+    final units = _distanceUnits(context);
     final routeStations = _routeResult?.calculatedRoute ?? [];
     final endTime = _legEndDateTime;
     final originTime = _originDateTime;
@@ -249,7 +250,7 @@ extension _NewEntryDraftLogic on _NewEntryPageState {
         ? _endController.text.trim()
         : (routeStations.isNotEmpty ? routeStations.last : '');
     final mileageVal = _useManualMileage
-        ? double.tryParse(_mileageController.text.trim()) ?? 0
+        ? (units.milesFromInput(_mileageController.text.trim()) ?? 0)
         : (_routeResult?.distance ?? 0);
     final tractionPayload = _buildTractionPayload();
     final commonPayload = {
@@ -338,6 +339,7 @@ extension _NewEntryDraftLogic on _NewEntryPageState {
     final destination = payload['leg_destination'] as String? ?? '';
     final tripRaw = payload['leg_trip'];
     final tripId = tripRaw is num ? tripRaw.toInt() : null;
+    final units = _distanceUnits(context);
 
     List<String> routeStations = [];
     RouteResult? restoredRouteResult;
@@ -416,14 +418,20 @@ extension _NewEntryDraftLogic on _NewEntryPageState {
         final miles = (payload['leg_distance'] as num?)?.toDouble();
         _mileageController.text = miles == null || miles == 0
             ? ''
-            : miles.toStringAsFixed(2);
+            : units.format(
+                miles,
+                decimals: 2,
+                includeUnit: false,
+              );
       } else {
         _startController.text =
             routeStations.isNotEmpty ? routeStations.first : '';
         _endController.text =
             routeStations.isNotEmpty ? routeStations.last : '';
         final dist = _routeResult?.distance ?? 0;
-        _mileageController.text = dist == 0 ? '' : dist.toStringAsFixed(2);
+        _mileageController.text = dist == 0
+            ? ''
+            : units.format(dist, decimals: 2, includeUnit: false);
       }
 
       final tractionRaw = data['tractionItems'];

lib/components/pages/new_entry/new_entry_drafts.dart

@@ -150,6 +150,7 @@ class _DraftListBodyState extends State<_DraftListBody> {
     final payload = draft.data['payload'];
     if (payload is! Map) return '';
     final map = Map<String, dynamic>.from(payload);
+    final units = context.read<DistanceUnitService>();
     final parts = <String>[];
     if ((map['leg_trip'] as int? ?? 0) != 0) {
       parts.add('Trip ${map['leg_trip']}');
@@ -164,7 +165,7 @@ class _DraftListBodyState extends State<_DraftListBody> {
         (map['leg_distance'] as num?)?.toDouble() ??
         (map['leg_mileage'] as num?)?.toDouble();
     if (mileage != null && mileage > 0) {
-      parts.add('${mileage.toStringAsFixed(1)} mi');
+      parts.add(units.format(mileage, decimals: 1));
     } else if (map['leg_route'] is List &&
         (map['leg_route'] as List).isNotEmpty) {
       parts.add('Route ${(map['leg_route'] as List).length} stops');
@@ -176,4 +177,3 @@ class _DraftListBodyState extends State<_DraftListBody> {
     return parts.join(' • ');
   }
 }
-

lib/components/pages/new_entry/new_entry_page.dart

@@ -51,6 +51,7 @@ class _NewEntryPageState extends State<NewEntryPage> {
   final DeepCollectionEquality _snapshotEquality =
       const DeepCollectionEquality();
   String? _activeDraftId;
+  DistanceUnit? _lastDistanceUnit;
 
   bool get _isEditing => widget.editLegId != null;
   bool get _draftPersistenceEnabled =>
@@ -100,6 +101,58 @@ class _NewEntryPageState extends State<NewEntryPage> {
     setState(fn);
   }
 
+  DistanceUnitService _distanceUnits(BuildContext context) =>
+      context.read<DistanceUnitService>();
+
+  String _formatDistance(
+    DistanceUnitService units,
+    double miles, {
+    int decimals = 1,
+    bool includeUnit = true,
+  }) {
+    return units.format(
+      miles,
+      decimals: decimals,
+      includeUnit: includeUnit,
+    );
+  }
+
+  String _manualMileageLabel(DistanceUnit unit) {
+    switch (unit) {
+      case DistanceUnit.milesDecimal:
+        return 'Mileage (mi)';
+      case DistanceUnit.kilometers:
+        return 'Mileage (km)';
+      case DistanceUnit.milesChains:
+        return 'Mileage (m.ch)';
+    }
+  }
+
+  double _manualMilesFromInput(DistanceUnitService units) {
+    return units.milesFromInput(_mileageController.text) ?? 0;
+  }
+
+  double _milesFromInputWithUnit(DistanceUnit unit) {
+    return DistanceFormatter(unit)
+            .parseInputMiles(_mileageController.text.trim()) ??
+        0;
+  }
+
+  void _syncManualFieldUnit(DistanceUnit currentUnit) {
+    if (!_useManualMileage) {
+      _lastDistanceUnit = currentUnit;
+      return;
+    }
+    final previousUnit = _lastDistanceUnit ?? currentUnit;
+    if (previousUnit == currentUnit) return;
+
+    final miles = _milesFromInputWithUnit(previousUnit);
+    final nextText = DistanceFormatter(currentUnit)
+        .format(miles, decimals: 2, includeUnit: false);
+    _mileageController.text = nextText;
+    _lastDistanceUnit = currentUnit;
+  }
+
   Widget _buildTripSelector(BuildContext context) {
     final trips = context.watch<DataService>().tripList;
     final sorted = [...trips]..sort((a, b) => b.tripId.compareTo(a.tripId));
@@ -224,9 +277,15 @@ class _NewEntryPageState extends State<NewEntryPage> {
       ),
     );
     if (result != null) {
+      final units = _distanceUnits(context);
       setState(() {
         _routeResult = result;
-        _mileageController.text = result.distance.toStringAsFixed(2);
+        _mileageController.text = _formatDistance(
+          units,
+          result.distance,
+          decimals: 2,
+          includeUnit: false,
+        );
         _useManualMileage = false;
       });
       _saveDraft();
@@ -426,6 +485,7 @@ class _NewEntryPageState extends State<NewEntryPage> {
       final endTime = DateTime.tryParse(json['leg_end_time'] ?? '');
       final routeStations = _parseRouteStations(json['leg_route']);
       final mileageVal = (json['leg_mileage'] as num?)?.toDouble() ?? 0.0;
+      final units = _distanceUnits(context);
       final useManual = routeStations.isEmpty;
       final routeResult = useManual
           ? null
@@ -484,7 +544,12 @@ class _NewEntryPageState extends State<NewEntryPage> {
         _endDelayController.text = endDelay.toString();
         _mileageController.text = mileageVal == 0
             ? ''
-            : mileageVal.toStringAsFixed(2);
+            : _formatDistance(
+                units,
+                mileageVal,
+                decimals: 2,
+                includeUnit: false,
+              );
         _tractionItems
           ..clear()
           ..addAll(tractionItems);
@@ -728,11 +793,15 @@ class _NewEntryPageState extends State<NewEntryPage> {
         key: _formKey,
         child: LayoutBuilder(
           builder: (context, constraints) {
+            final distanceUnitService = context.watch<DistanceUnitService>();
+            final currentDistanceUnit = distanceUnitService.unit;
+            _syncManualFieldUnit(currentDistanceUnit);
             final twoCol = !isMobile && constraints.maxWidth > 1000;
             final tractionEmpty = _tractionItems.length == 1;
             final mileageEmpty = !_useManualMileage && _routeResult == null;
             final balancePanels = twoCol && tractionEmpty && mileageEmpty;
             final balancedHeight = balancePanels ? 165.0 : null;
+            final mileageLabel = _manualMileageLabel(currentDistanceUnit);
 
             final entryPanel = _section('Entry', [
               Row(
@@ -948,9 +1017,13 @@ class _NewEntryPageState extends State<NewEntryPage> {
                     keyboardType: const TextInputType.numberWithOptions(
                       decimal: true,
                     ),
-                    decoration: const InputDecoration(
+                    decoration: InputDecoration(
-                      labelText: 'Mileage (mi)',
+                      labelText: mileageLabel,
-                      border: OutlineInputBorder(),
+                      helperText: currentDistanceUnit ==
+                              DistanceUnit.milesChains
+                          ? 'Enter as miles.chains (e.g., 12.40 for 12m 40c)'
+                          : null,
+                      border: const OutlineInputBorder(),
                     ),
                   )
                 else if (_routeResult != null)
@@ -958,7 +1031,11 @@ class _NewEntryPageState extends State<NewEntryPage> {
                     contentPadding: EdgeInsets.zero,
                     title: const Text('Calculated mileage'),
                     subtitle: Text(
-                      '${_routeResult!.distance.toStringAsFixed(2)} mi',
+                      _formatDistance(
+                        distanceUnitService,
+                        _routeResult!.distance,
+                        decimals: 2,
+                      ),
                     ),
                   )
                 else
@@ -973,7 +1050,17 @@ class _NewEntryPageState extends State<NewEntryPage> {
                 label: Text(_useManualMileage ? 'Manual' : 'Automatic'),
                 selected: _useManualMileage,
                 onSelected: (val) {
-                  setState(() => _useManualMileage = val);
+                  setState(() {
+                    _useManualMileage = val;
+                    if (val && _routeResult != null) {
+                      _mileageController.text = _formatDistance(
+                        distanceUnitService,
+                        _routeResult!.distance,
+                        decimals: 2,
+                        includeUnit: false,
+                      );
+                    }
+                  });
                   _saveDraft();
                   _scheduleMatchUpdate();
                 },

lib/components/pages/new_entry/new_entry_submit_logic.dart

@@ -4,11 +4,12 @@ extension _NewEntrySubmitLogic on _NewEntryPageState {
   Future<bool> _validateRequiredFields() async {
     final missing = <String>[];
 
+    final units = _distanceUnits(context);
     if (_useManualMileage) {
       if (_startController.text.trim().isEmpty) missing.add('From');
       if (_endController.text.trim().isEmpty) missing.add('To');
       final mileageText = _mileageController.text.trim();
-      if (double.tryParse(mileageText) == null) {
+      if (mileageText.isEmpty || units.milesFromInput(mileageText) == null) {
         missing.add('Mileage');
       }
     } else {
@@ -58,8 +59,9 @@ extension _NewEntrySubmitLogic on _NewEntryPageState {
     final endVal = _useManualMileage
         ? _endController.text.trim()
         : (routeStations.isNotEmpty ? routeStations.last : '');
+    final units = _distanceUnits(context);
     final mileageVal = _useManualMileage
-        ? double.tryParse(_mileageController.text.trim()) ?? 0
+        ? (units.milesFromInput(_mileageController.text.trim()) ?? 0)
         : (_routeResult?.distance ?? 0);
     final tractionPayload = _buildTractionPayload();
     final endTime = _legEndDateTime;

lib/components/pages/settings.dart

@@ -5,6 +5,7 @@ import 'package:go_router/go_router.dart';
 import 'package:http/http.dart' as http;
 import 'package:mileograph_flutter/services/authservice.dart';
 import 'package:mileograph_flutter/services/api_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:mileograph_flutter/services/endpoint_service.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
 import 'package:provider/provider.dart';
@@ -175,10 +176,11 @@ class _SettingsPageState extends State<SettingsPage> {
   @override
   Widget build(BuildContext context) {
     final endpointService = context.watch<EndpointService>();
+    final distanceUnitService = context.watch<DistanceUnitService>();
     final loggedIn = context.select<AuthService, bool>(
       (auth) => auth.isLoggedIn,
     );
-    if (!endpointService.isLoaded) {
+    if (!endpointService.isLoaded || !distanceUnitService.isLoaded) {
       return const Scaffold(
         body: Center(child: CircularProgressIndicator()),
       );
@@ -204,6 +206,34 @@ class _SettingsPageState extends State<SettingsPage> {
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
+            Text(
+              'Distance units',
+              style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                    fontWeight: FontWeight.w700,
+                  ),
+            ),
+            const SizedBox(height: 8),
+            Text(
+              'Choose how distances are displayed across the app.',
+              style: Theme.of(context).textTheme.bodySmall,
+            ),
+            const SizedBox(height: 12),
+            SegmentedButton<DistanceUnit>(
+              segments: DistanceUnit.values
+                  .map(
+                    (unit) => ButtonSegment<DistanceUnit>(
+                      value: unit,
+                      label: Text(unit.label),
+                    ),
+                  )
+                  .toList(),
+              selected: {distanceUnitService.unit},
+              onSelectionChanged: (selection) {
+                final next = selection.first;
+                distanceUnitService.setUnit(next);
+              },
+            ),
+            const SizedBox(height: 24),
             Text(
               'API endpoint',
               style: Theme.of(context).textTheme.titleMedium?.copyWith(

lib/components/pages/stats.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:intl/intl.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 
 class StatsPage extends StatefulWidget {
@@ -12,7 +13,6 @@ class StatsPage extends StatefulWidget {
 }
 
 class _StatsPageState extends State<StatsPage> {
-  final NumberFormat _mileageFormat = NumberFormat('#,##0.##');
   final NumberFormat _countFormat = NumberFormat.decimalPattern();
 
   @override
@@ -30,16 +30,20 @@ class _StatsPageState extends State<StatsPage> {
   @override
   Widget build(BuildContext context) {
     final data = context.watch<DataService>();
+    final distanceUnits = context.watch<DistanceUnitService>();
     return Scaffold(
       appBar: AppBar(title: const Text('Stats')),
       body: RefreshIndicator(
         onRefresh: () => _loadStats(force: true),
-        child: _buildContent(data),
+        child: _buildContent(data, distanceUnits),
       ),
     );
   }
 
-  Widget _buildContent(DataService data) {
+  Widget _buildContent(
+    DataService data,
+    DistanceUnitService distanceUnits,
+  ) {
     final stats = data.aboutStats;
     final loading = data.isAboutStatsLoading;
 
@@ -79,13 +83,14 @@ class _StatsPageState extends State<StatsPage> {
       itemBuilder: (context, index) {
         return Padding(
           padding: EdgeInsets.only(bottom: index == years.length - 1 ? 0 : 12),
-          child: _buildYearCard(context, years[index]),
+          child: _buildYearCard(context, years[index], distanceUnits),
         );
       },
     );
   }
 
-  Widget _buildYearCard(BuildContext context, StatsYear year) {
+  Widget _buildYearCard(
+      BuildContext context, StatsYear year, DistanceUnitService distanceUnits) {
     final theme = Theme.of(context);
     return Card(
       child: Padding(
@@ -109,7 +114,7 @@ class _StatsPageState extends State<StatsPage> {
                     _buildInfoChip(
                       context,
                       label: 'Mileage',
-                      value: '${_mileageFormat.format(year.mileage)} mi',
+                      value: distanceUnits.format(year.mileage, decimals: 1),
                     ),
                     _buildInfoChip(
                       context,
@@ -126,25 +131,29 @@ class _StatsPageState extends State<StatsPage> {
               title: 'Top classes',
               items: year.topClasses,
               emptyLabel: 'No class data',
-              itemBuilder: (item, index) => ListTile(
+                itemBuilder: (item, index) => ListTile(
-                dense: true,
+                  dense: true,
-                contentPadding: const EdgeInsets.symmetric(horizontal: 8),
+                  contentPadding: const EdgeInsets.symmetric(horizontal: 8),
-                title: Text(item.locoClass),
+                  title: Text(item.locoClass),
-                trailing: Text('${_mileageFormat.format(item.mileage)} mi'),
+                  trailing: Text(
+                    distanceUnits.format(item.mileage, decimals: 1),
+                  ),
+                ),
               ),
-            ),
             _buildSection<StatsNetworkMileage>(
               context,
               title: 'Top networks',
               items: year.topNetworks,
               emptyLabel: 'No network data',
-              itemBuilder: (item, index) => ListTile(
+                itemBuilder: (item, index) => ListTile(
-                dense: true,
+                  dense: true,
-                contentPadding: const EdgeInsets.symmetric(horizontal: 8),
+                  contentPadding: const EdgeInsets.symmetric(horizontal: 8),
-                title: Text(item.network),
+                  title: Text(item.network),
-                trailing: Text('${_mileageFormat.format(item.mileage)} mi'),
+                  trailing: Text(
+                    distanceUnits.format(item.mileage, decimals: 1),
+                  ),
+                ),
               ),
-            ),
             _buildSection<StatsStationVisits>(
               context,
               title: 'Top stations',

lib/components/pages/traction/traction.dart

@@ -6,6 +6,7 @@ import 'package:go_router/go_router.dart';
 import 'package:mileograph_flutter/components/traction/traction_card.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 

lib/components/pages/traction/traction_page.dart

@@ -639,6 +639,7 @@ class _TractionPageState extends State<TractionPage> {
 
   Widget _buildClassStatsCard(BuildContext context) {
     final scheme = Theme.of(context).colorScheme;
+    final distanceUnits = context.watch<DistanceUnitService>();
     if (_classStatsLoading) {
       return Card(
         child: Padding(
@@ -721,9 +722,27 @@ class _TractionPageState extends State<TractionPage> {
               children: [
                 _metricTile('Had', hadCount),
                 _metricTile('Entries', entriesWithClass),
-                _metricTile('Avg mi / loco had', avgMileagePerLoco.toStringAsFixed(2)),
+                _metricTile(
-                _metricTile('Avg mi / entry', avgMileagePerEntry.toStringAsFixed(2)),
+                  'Avg distance / loco had',
-                _metricTile('Total mileage', totalMileage.toStringAsFixed(2)),
+                  distanceUnits.format(
+                    avgMileagePerLoco,
+                    decimals: 2,
+                  ),
+                ),
+                _metricTile(
+                  'Avg distance / entry',
+                  distanceUnits.format(
+                    avgMileagePerEntry,
+                    decimals: 2,
+                  ),
+                ),
+                _metricTile(
+                  'Total distance',
+                  distanceUnits.format(
+                    totalMileage,
+                    decimals: 2,
+                  ),
+                ),
               ],
             ),
             const SizedBox(height: 12),

lib/components/pages/trips.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 
 class TripsPage extends StatefulWidget {
@@ -99,6 +100,7 @@ class _TripsPageState extends State<TripsPage> {
   @override
   Widget build(BuildContext context) {
     final data = context.watch<DataService>();
+    final distanceUnits = context.watch<DistanceUnitService>();
     final tripDetails = data.tripDetails;
     final tripSummaries = data.tripList;
     final summaryById = {
@@ -188,7 +190,8 @@ class _TripsPageState extends State<TripsPage> {
             return Card(
               child: ListTile(
                 title: Text(trip.tripName),
-                subtitle: Text('${trip.tripMileage.toStringAsFixed(1)} mi'),
+                subtitle:
+                    Text(distanceUnits.format(trip.tripMileage, decimals: 1)),
               ),
             );
           }
@@ -206,6 +209,7 @@ class _TripsPageState extends State<TripsPage> {
     TripDetail trip,
     TripSummary? summary,
   ) {
+    final distanceUnits = context.watch<DistanceUnitService>();
     final legs = trip.legs;
     final legCount =
         trip.legCount > 0 ? trip.legCount : summary?.legCount ?? legs.length;
@@ -245,18 +249,12 @@ class _TripsPageState extends State<TripsPage> {
                   crossAxisAlignment: CrossAxisAlignment.end,
                   children: [
                     Text(
-                      trip.mileage.toStringAsFixed(1),
+                      distanceUnits.format(trip.mileage, decimals: 1),
                       style:
                           Theme.of(context).textTheme.headlineSmall?.copyWith(
                         fontWeight: FontWeight.w800,
                       ),
                     ),
-                    Text(
-                      'miles',
-                      style: Theme.of(context).textTheme.labelMedium?.copyWith(
-                        color: Theme.of(context).textTheme.bodySmall?.color,
-                      ),
-                    ),
                   ],
                 ),
               ],
@@ -367,6 +365,7 @@ class _TripsPageState extends State<TripsPage> {
   }
 
   void _showTripDetail(BuildContext context, TripDetail trip) {
+    final distanceUnits = context.read<DistanceUnitService>();
     showModalBottomSheet(
       context: context,
       isScrollControlled: true,
@@ -491,7 +490,9 @@ class _TripsPageState extends State<TripsPage> {
                           ),
                         ],
                         const SizedBox(width: 4),
-                        Text('${trip.mileage.toStringAsFixed(1)} mi'),
+                        Text(
+                          distanceUnits.format(trip.mileage, decimals: 1),
+                        ),
                       ],
                     ),
                     const SizedBox(height: 8),
@@ -506,7 +507,12 @@ class _TripsPageState extends State<TripsPage> {
                             title: Text('${leg.start} → ${leg.end}'),
                             subtitle: Text(_formatDate(leg.beginTime)),
                             trailing: Text(
-                              leg.mileage?.toStringAsFixed(1) ?? '-',
+                              leg.mileage == null
+                                  ? '-'
+                                  : distanceUnits.format(
+                                      leg.mileage!,
+                                      decimals: 1,
+                                    ),
                               style: Theme.of(context).textTheme.labelLarge
                                   ?.copyWith(fontWeight: FontWeight.bold),
                             ),
@@ -529,6 +535,7 @@ class _TripsPageState extends State<TripsPage> {
     TripDetail trip,
     TripSummary? summary,
   ) {
+    final distanceUnits = context.read<DistanceUnitService>();
     showModalBottomSheet(
       context: context,
       isScrollControlled: true,
@@ -561,7 +568,9 @@ class _TripsPageState extends State<TripsPage> {
                               ?.copyWith(fontWeight: FontWeight.bold),
                         ),
                         const Spacer(),
-                        Text('${trip.mileage.toStringAsFixed(1)} mi'),
+                        Text(
+                          distanceUnits.format(trip.mileage, decimals: 1),
+                        ),
                       ],
                     ),
                     const SizedBox(height: 8),

lib/components/traction/traction_card.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
+import 'package:provider/provider.dart';
 
 class TractionCard extends StatelessWidget {
   const TractionCard({
@@ -28,6 +30,7 @@ class TractionCard extends StatelessWidget {
     final domain = loco.domain ?? '';
     final hasMileageOrTrips = _hasMileageOrTrips(loco);
     final statusColors = _statusChipColors(context, status);
+    final distanceUnits = context.watch<DistanceUnitService>();
 
     return Card(
       child: Padding(
@@ -151,8 +154,11 @@ class TractionCard extends StatelessWidget {
               children: [
                 _statPill(
                   context,
-                  label: 'Miles',
+                  label: 'Distance',
-                  value: _formatNumber(loco.mileage),
+                  value: distanceUnits.format(
+                    loco.mileage ?? 0,
+                    decimals: 1,
+                  ),
                 ),
                 _statPill(
                   context,
@@ -203,6 +209,7 @@ Future<void> showTractionDetails(
   LocoSummary loco,
 ) async {
   final hasMileageOrTrips = _hasMileageOrTrips(loco);
+  final distanceUnits = context.read<DistanceUnitService>();
   await showModalBottomSheet(
     context: context,
     isScrollControlled: true,
@@ -275,7 +282,10 @@ Future<void> showTractionDetails(
                       _detailRow(
                         context,
                         'Mileage',
-                        _formatNumber(loco.mileage ?? 0),
+                        distanceUnits.format(
+                          loco.mileage ?? 0,
+                          decimals: 1,
+                        ),
                       ),
                       _detailRow(
                         context,
@@ -368,8 +378,3 @@ bool _hasMileageOrTrips(LocoSummary loco) {
   final trips = loco.trips ?? loco.journeys ?? 0;
   return mileage > 0 || trips > 0;
 }
-
-String _formatNumber(double? value) {
-  if (value == null) return '0';
-  return value.toStringAsFixed(1);
-}

lib/services/distance_unit_service.dart

@@ -0,0 +1,211 @@
+import 'package:flutter/foundation.dart';
+import 'package:intl/intl.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+enum DistanceUnit {
+  milesDecimal,
+  milesChains,
+  kilometers,
+}
+
+extension DistanceUnitLabels on DistanceUnit {
+  String get label {
+    switch (this) {
+      case DistanceUnit.milesDecimal:
+        return 'Miles (decimal)';
+      case DistanceUnit.milesChains:
+        return 'Miles & chains';
+      case DistanceUnit.kilometers:
+        return 'Kilometers';
+    }
+  }
+
+  String get shortLabel {
+    switch (this) {
+      case DistanceUnit.milesDecimal:
+        return 'mi';
+      case DistanceUnit.milesChains:
+        return 'm.ch';
+      case DistanceUnit.kilometers:
+        return 'km';
+    }
+  }
+
+  String get _prefsValue => toString().split('.').last;
+
+  static DistanceUnit fromPrefs(String raw) {
+    return DistanceUnit.values.firstWhere(
+      (u) => u._prefsValue == raw,
+      orElse: () => DistanceUnit.milesDecimal,
+    );
+  }
+}
+
+class DistanceUnitService extends ChangeNotifier {
+  static const _prefsKey = 'distance_unit';
+  static const double kmPerMile = 1.609344;
+  static const double chainsPerMile = 80.0;
+
+  DistanceUnitService() {
+    _load();
+  }
+
+  DistanceUnit _unit = DistanceUnit.milesDecimal;
+  bool _loaded = false;
+
+  DistanceUnit get unit => _unit;
+  bool get isLoaded => _loaded;
+
+  Future<void> _load() async {
+    final prefs = await SharedPreferences.getInstance();
+    final saved = prefs.getString(_prefsKey);
+    if (saved != null && saved.trim().isNotEmpty) {
+      _unit = DistanceUnitLabels.fromPrefs(saved.trim());
+    }
+    _loaded = true;
+    notifyListeners();
+  }
+
+  Future<void> setUnit(DistanceUnit unit) async {
+    _unit = unit;
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setString(_prefsKey, unit._prefsValue);
+    notifyListeners();
+  }
+
+  double? milesFromInput(String input) =>
+      DistanceFormatter(_unit).parseInputMiles(input);
+
+  String format(double miles,
+          {int decimals = 1, bool includeUnit = true}) =>
+      DistanceFormatter(_unit)
+          .format(miles, decimals: decimals, includeUnit: includeUnit);
+
+  double toDisplay(double miles, {int decimals = 1}) =>
+      DistanceFormatter(_unit).convertMiles(miles, decimals: decimals);
+}
+
+class DistanceFormatter {
+  DistanceFormatter(this.unit);
+
+  final DistanceUnit unit;
+
+  String format(double miles,
+      {int decimals = 1, bool includeUnit = true}) {
+    decimals = decimals.clamp(1, 2);
+    if (unit == DistanceUnit.milesChains) {
+      // Always show chains with two decimals.
+      decimals = 2;
+    }
+    switch (unit) {
+      case DistanceUnit.milesDecimal:
+        final value = _numberFormat(decimals).format(miles);
+        return includeUnit ? '$value mi' : value;
+      case DistanceUnit.kilometers:
+        final kms = miles * DistanceUnitService.kmPerMile;
+        final value = _numberFormat(decimals).format(kms);
+        return includeUnit ? '$value km' : value;
+      case DistanceUnit.milesChains:
+        final value = _formatMilesChains(miles);
+        return includeUnit ? '$value mi' : value;
+    }
+  }
+
+  double convertMiles(double miles, {int decimals = 1}) {
+    decimals = decimals.clamp(1, 2);
+    switch (unit) {
+      case DistanceUnit.milesDecimal:
+        return double.parse(miles.toStringAsFixed(decimals));
+      case DistanceUnit.kilometers:
+        final kms = miles * DistanceUnitService.kmPerMile;
+        return double.parse(kms.toStringAsFixed(decimals));
+      case DistanceUnit.milesChains:
+        // Return miles again; chains representation handled by format.
+        return double.parse(miles.toStringAsFixed(decimals));
+    }
+  }
+
+  double milesFromDisplayValue(double value) {
+    switch (unit) {
+      case DistanceUnit.milesDecimal:
+        return value;
+      case DistanceUnit.kilometers:
+        return value / DistanceUnitService.kmPerMile;
+      case DistanceUnit.milesChains:
+        // Value already represents miles when parsed via parseMilesChains.
+        return value;
+    }
+  }
+
+  double? parseInputMiles(String input) {
+    final trimmed = input.trim();
+    if (trimmed.isEmpty) return null;
+    switch (unit) {
+      case DistanceUnit.milesDecimal:
+        return double.tryParse(trimmed.replaceAll(',', ''));
+      case DistanceUnit.kilometers:
+        final km = double.tryParse(trimmed.replaceAll(',', ''));
+        if (km == null) return null;
+        return km / DistanceUnitService.kmPerMile;
+      case DistanceUnit.milesChains:
+        return _parseMilesChains(trimmed);
+    }
+  }
+
+  NumberFormat _numberFormat(int decimals) {
+    final pattern =
+        decimals == 1 ? '#,##0.0' : '#,##0.00';
+    return NumberFormat(pattern);
+  }
+
+  String _formatMilesChains(double miles, {int decimals = 1}) {
+    final totalChains = miles * DistanceUnitService.chainsPerMile;
+    var milesPart = totalChains ~/ DistanceUnitService.chainsPerMile;
+    final chainRemainder =
+        totalChains - (milesPart * DistanceUnitService.chainsPerMile);
+
+    // Always show chains as two digits (00-79), rounded to the nearest chain.
+    var roundedChains = chainRemainder.roundToDouble();
+    if (roundedChains >= DistanceUnitService.chainsPerMile) {
+      milesPart += 1;
+      roundedChains -= DistanceUnitService.chainsPerMile;
+    }
+    final chainText = NumberFormat('00').format(roundedChains);
+    return '$milesPart.$chainText';
+  }
+
+  double? _parseMilesChains(String raw) {
+    final cleaned = raw
+        .toLowerCase()
+        .replaceAll(',', '')
+        .replaceAll('m', '.')
+        .replaceAll('c', '.')
+        .replaceAll(RegExp(r'\s+'), '.')
+        .replaceAll(RegExp(r'\.+'), '.')
+        .trim();
+    if (cleaned.isEmpty) return null;
+
+    final parts = cleaned.split('.');
+    if (parts.isEmpty) return null;
+
+    final milesPart =
+        int.tryParse(parts[0].isEmpty ? '0' : parts[0]);
+    if (milesPart == null) return null;
+    double chainsPart = 0;
+    if (parts.length >= 2) {
+      final chainRaw = parts
+          .sublist(1)
+          .join()
+          .trim();
+      if (chainRaw.isNotEmpty) {
+        final parsedChains = double.tryParse(chainRaw);
+        if (parsedChains == null) return null;
+        chainsPart = parsedChains;
+      }
+    }
+    final totalMiles =
+        milesPart +
+        (chainsPart / DistanceUnitService.chainsPerMile);
+    return totalMiles;
+  }
+}

pubspec.yaml

@@ -16,7 +16,7 @@ publish_to: "none" # Remove this line if you wish to publish to pub.dev
 # https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
 # In Windows, build-name is used as the major, minor, and patch parts
 # of the product and file versions while build-number is used as the build suffix.
-version: 0.5.0+1
+version: 0.5.1+1
 
 environment:
   sdk: ^3.8.1
@@ -103,6 +103,6 @@ flutter_launcher_icons:
   android: true
   ios: true
   image_path: assets/icons/app_icon.png
-  adaptive_icon_background: "#ffffff"
+  adaptive_icon_background: "#000000"
   adaptive_icon_foreground: assets/icons/app_icon.png
   min_sdk_android: 21