diff --git a/app/lib/list_extension.dart b/app/lib/list_extension.dart
index a2452b02..7b7fa674 100644
--- a/app/lib/list_extension.dart
+++ b/app/lib/list_extension.dart
@@ -1,7 +1,7 @@
 import 'dart:math' as math;
 
 import 'package:collection/collection.dart';
-import 'package:nc_photos/int_extension.dart';
+import 'package:np_math/np_math.dart';
 
 extension ListExtension<T> on List<T> {
   Iterable<T> takeIndex(List<int> indexes) => indexes.map((e) => this[e]);
diff --git a/app/lib/reverse_geocoder.dart b/app/lib/reverse_geocoder.dart
index 5b7133b3..0295e7e4 100644
--- a/app/lib/reverse_geocoder.dart
+++ b/app/lib/reverse_geocoder.dart
@@ -4,10 +4,10 @@ import 'package:collection/collection.dart';
 import 'package:kdtree/kdtree.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/entity/file.dart';
-import 'package:nc_photos/math_util.dart' as math_util;
 import 'package:nc_photos/mobile/platform.dart'
     if (dart.library.html) 'package:nc_photos/web/platform.dart' as platform;
 import 'package:np_codegen/np_codegen.dart';
+import 'package:np_math/np_math.dart';
 import 'package:sqlite3/common.dart';
 import 'package:to_string/to_string.dart';
 
@@ -58,10 +58,10 @@ class ReverseGeocoder {
     _log.info("[call] Nearest point, (lat: $nearestLatF, lng: $nearestLngF)");
     try {
       final distance = _distanceInKm(
-        math_util.degToRad(latitude),
-        math_util.degToRad(longitude),
-        math_util.degToRad(nearestLatF),
-        math_util.degToRad(nearestLngF),
+        degToRad(latitude),
+        degToRad(longitude),
+        degToRad(nearestLatF),
+        degToRad(nearestLngF),
       );
       _log.info(
           "[call] (lat: ${latitude.toStringAsFixed(3)}, lng: ${longitude.toStringAsFixed(3)}) <-> (lat: $nearestLatF, lng: $nearestLngF) = ${distance.toStringAsFixed(3)}km");
diff --git a/app/lib/throttler.dart b/app/lib/throttler.dart
index 9aeb6779..4f54c604 100644
--- a/app/lib/throttler.dart
+++ b/app/lib/throttler.dart
@@ -2,8 +2,8 @@ import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:logging/logging.dart';
-import 'package:nc_photos/int_util.dart';
 import 'package:np_codegen/np_codegen.dart';
+import 'package:np_math/np_math.dart';
 
 part 'throttler.g.dart';
 
diff --git a/app/lib/widget/photo_date_time_edit_dialog.dart b/app/lib/widget/photo_date_time_edit_dialog.dart
index b307c5fb..be7dcdb3 100644
--- a/app/lib/widget/photo_date_time_edit_dialog.dart
+++ b/app/lib/widget/photo_date_time_edit_dialog.dart
@@ -1,8 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/app_localizations.dart';
-import 'package:nc_photos/num_extension.dart';
 import 'package:np_codegen/np_codegen.dart';
+import 'package:np_math/np_math.dart';
 
 part 'photo_date_time_edit_dialog.g.dart';
 
diff --git a/app/lib/widget/slideshow_dialog.dart b/app/lib/widget/slideshow_dialog.dart
index 34017071..228f3046 100644
--- a/app/lib/widget/slideshow_dialog.dart
+++ b/app/lib/widget/slideshow_dialog.dart
@@ -2,9 +2,9 @@ import 'package:flutter/material.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/app_localizations.dart';
 import 'package:nc_photos/k.dart' as k;
-import 'package:nc_photos/num_extension.dart';
 import 'package:nc_photos/snack_bar_manager.dart';
 import 'package:np_codegen/np_codegen.dart';
+import 'package:np_math/np_math.dart';
 import 'package:np_ui/np_ui.dart';
 import 'package:to_string/to_string.dart';
 
diff --git a/app/pubspec.lock b/app/pubspec.lock
index d0f2ac92..8c9b36cf 100644
--- a/app/pubspec.lock
+++ b/app/pubspec.lock
@@ -983,6 +983,13 @@ packages:
       relative: true
     source: path
     version: "1.0.0"
+  np_math:
+    dependency: "direct main"
+    description:
+      path: "../np_math"
+      relative: true
+    source: path
+    version: "1.0.0"
   np_ui:
     dependency: "direct main"
     description:
diff --git a/app/pubspec.yaml b/app/pubspec.yaml
index 8580ddf1..1386c4cd 100644
--- a/app/pubspec.yaml
+++ b/app/pubspec.yaml
@@ -105,6 +105,8 @@ dependencies:
     path: ../np_common
   np_log:
     path: ../np_log
+  np_math:
+    path: ../np_math
   np_ui:
     path: ../np_ui
   octo_image: any
diff --git a/app/test/entity/file/file_cache_manager_test.dart b/app/test/entity/file/file_cache_manager_test.dart
index 4f11798b..07b3d7d5 100644
--- a/app/test/entity/file/file_cache_manager_test.dart
+++ b/app/test/entity/file/file_cache_manager_test.dart
@@ -3,9 +3,9 @@ import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/entity/file/data_source.dart';
 import 'package:nc_photos/entity/file/file_cache_manager.dart';
 import 'package:nc_photos/entity/sqlite/database.dart' as sql;
-import 'package:nc_photos/int_extension.dart';
 import 'package:nc_photos/list_extension.dart';
 import 'package:np_common/or_null.dart';
+import 'package:np_math/np_math.dart';
 import 'package:test/test.dart';
 
 import '../../mock_type.dart';
diff --git a/app/test/iterable_extension_test.dart b/app/test/iterable_extension_test.dart
index e7279884..c94cb705 100644
--- a/app/test/iterable_extension_test.dart
+++ b/app/test/iterable_extension_test.dart
@@ -1,5 +1,5 @@
-import 'package:nc_photos/int_extension.dart';
 import 'package:nc_photos/iterable_extension.dart';
+import 'package:np_math/np_math.dart';
 import 'package:quiver/core.dart';
 import 'package:test/test.dart';
 import 'package:tuple/tuple.dart';
diff --git a/np_math/.gitignore b/np_math/.gitignore
new file mode 100644
index 00000000..3cceda55
--- /dev/null
+++ b/np_math/.gitignore
@@ -0,0 +1,7 @@
+# https://dart.dev/guides/libraries/private-files
+# Created by `dart pub`
+.dart_tool/
+
+# Avoid committing pubspec.lock for library packages; see
+# https://dart.dev/guides/libraries/private-files#pubspeclock.
+pubspec.lock
diff --git a/np_math/analysis_options.yaml b/np_math/analysis_options.yaml
new file mode 100644
index 00000000..f92d2567
--- /dev/null
+++ b/np_math/analysis_options.yaml
@@ -0,0 +1 @@
+include: package:np_lints/np.yaml
diff --git a/np_math/lib/np_math.dart b/np_math/lib/np_math.dart
new file mode 100644
index 00000000..6f27d671
--- /dev/null
+++ b/np_math/lib/np_math.dart
@@ -0,0 +1,6 @@
+library np_math;
+
+export 'src/int_extension.dart';
+export 'src/int_util.dart';
+export 'src/math_util.dart';
+export 'src/num_extension.dart';
diff --git a/app/lib/int_extension.dart b/np_math/lib/src/int_extension.dart
similarity index 100%
rename from app/lib/int_extension.dart
rename to np_math/lib/src/int_extension.dart
diff --git a/app/lib/int_util.dart b/np_math/lib/src/int_util.dart
similarity index 100%
rename from app/lib/int_util.dart
rename to np_math/lib/src/int_util.dart
diff --git a/app/lib/math_util.dart b/np_math/lib/src/math_util.dart
similarity index 100%
rename from app/lib/math_util.dart
rename to np_math/lib/src/math_util.dart
diff --git a/app/lib/num_extension.dart b/np_math/lib/src/num_extension.dart
similarity index 100%
rename from app/lib/num_extension.dart
rename to np_math/lib/src/num_extension.dart
diff --git a/np_math/pubspec.yaml b/np_math/pubspec.yaml
new file mode 100644
index 00000000..d95ef7ef
--- /dev/null
+++ b/np_math/pubspec.yaml
@@ -0,0 +1,13 @@
+name: np_math
+description: A starting point for Dart libraries or applications.
+version: 1.0.0
+# repository: https://github.com/my_org/my_repo
+publish_to: none
+
+environment:
+  sdk: '>=2.19.6 <3.0.0'
+
+dev_dependencies:
+  np_lints:
+    path: ../np_lints
+  test: ^1.21.0
diff --git a/app/test/int_extension_test.dart b/np_math/test/int_extension_test.dart
similarity index 96%
rename from app/test/int_extension_test.dart
rename to np_math/test/int_extension_test.dart
index de01689e..59db9c0f 100644
--- a/app/test/int_extension_test.dart
+++ b/np_math/test/int_extension_test.dart
@@ -1,4 +1,4 @@
-import 'package:nc_photos/int_extension.dart';
+import 'package:np_math/src/int_extension.dart';
 import 'package:test/test.dart';
 
 void main() {
diff --git a/app/test/math_util_test.dart b/np_math/test/math_util_test.dart
similarity index 51%
rename from app/test/math_util_test.dart
rename to np_math/test/math_util_test.dart
index a11773f9..4e5d835c 100644
--- a/app/test/math_util_test.dart
+++ b/np_math/test/math_util_test.dart
@@ -1,15 +1,15 @@
 import 'dart:math' as math;
 
-import 'package:nc_photos/math_util.dart' as math_util;
+import 'package:np_math/src/math_util.dart';
 import 'package:test/test.dart';
 
 void main() {
   group("math_util", () {
     test("degToRad", () {
-      expect(math_util.degToRad(90), closeTo(1.570796, 1e-6));
+      expect(degToRad(90), closeTo(1.570796, 1e-6));
     });
     test("radToDeg", () {
-      expect(math_util.radToDeg(math.pi), 180);
+      expect(radToDeg(math.pi), 180);
     });
   });
 }
diff --git a/app/test/num_extension_test.dart b/np_math/test/num_extension_test.dart
similarity index 97%
rename from app/test/num_extension_test.dart
rename to np_math/test/num_extension_test.dart
index 59b4e8cb..88c1a3f3 100644
--- a/app/test/num_extension_test.dart
+++ b/np_math/test/num_extension_test.dart
@@ -1,4 +1,4 @@
-import 'package:nc_photos/num_extension.dart';
+import 'package:np_math/src/num_extension.dart';
 import 'package:test/test.dart';
 
 void main() {