NumberConverter app

Number System Converter & Calculator for Android#

An offline, privacy-focused converter for Binary, Octal, Decimal, and Hexadecimal — built with Jetpack Compose and Material 3. Every conversion and calculation comes with a step-by-step explanation of how the answer was reached.

Features#

• Convert Any Base — Binary, Octal, Decimal, and Hexadecimal in all 12 directions
• Fractional Support — converts values with a fractional part, not just integers
• Step-by-Step Explanations — every conversion opens a sheet showing positional notation, the division method, remainders, and the final result
• Mixed-Base Calculator — add, subtract, multiply, and divide across different bases (e.g. 1010₂ + 17₁₀), with the result in any base you pick
• Calculation Breakdowns — the calculator explains operand conversion, the arithmetic, and the conversion back
• History & Bookmarks — every conversion is saved, searchable, and can be starred for later
• Material 3 Design — dark mode, optional dynamic colors, and adjustable font size
• 100% Offline — no permissions, no network, no ads, no tracking, no analytics

Download#

You can download the latest APK from here

Check out the releases section for more details.

Screenshots#

Shots	Shots	Shots

Architecture#

Number Converter follows Clean Architecture principles with the MVVM pattern:

app/src/main/java/com/rejowan/numberconverter/
├── data/                      # Data layer
│   ├── converter/             # BaseConverter + per-base converters, explanation generators
│   ├── local/
│   │   ├── database/          # Room database, DAO, entities
│   │   └── datastore/         # PreferencesManager
│   └── repository/            # Repository implementations
│
├── domain/                    # Domain layer
│   ├── model/                 # NumberBase, Operation, Explanation, HistoryItem
│   ├── repository/            # Repository interfaces
│   └── usecase/               # converter / calculator / history / settings
│
├── presentation/              # Presentation layer (UI)
│   ├── common/                # Shared components, theme, util
│   ├── converter/             # Converter screen, state, components
│   ├── calculator/            # Calculator screen, state, components
│   ├── settings/              # Settings screen, state, components
│   ├── onboarding/            # First-run onboarding
│   ├── home/                  # Bottom-nav host
│   ├── navigation/            # Parent + bottom-nav graphs
│   └── main/                  # MainActivity
│
├── di/                        # Koin dependency injection
└── util/                      # Utilities

Tech Stack#

• UI Framework: Jetpack Compose (100% Compose UI)
• Language: Kotlin (100%)
• Architecture: MVVM + Clean Architecture
• Dependency Injection: Koin
• Database: Room (KSP)
• Preferences: DataStore
• Async: Kotlin Coroutines + Flow
• Navigation: Jetpack Navigation Compose (type-safe routes via Kotlin Serialization)
• Design: Material 3 with dynamic color support
• Precision: BigInteger / BigDecimal for arbitrary-precision conversion
• Testing: JUnit, MockK, Turbine

Requirements#

• Minimum SDK: API 24 (Android 7.0 Nougat)
• Target SDK: API 37
• Compile SDK: API 37
• Gradle: 9.7.0
• AGP: 9.2.1
• Kotlin: 2.4.10
• Java: 17

Permissions#

None. The app declares no permissions at all — not even INTERNET.

Note: This app does not collect or transmit any user data.

Build & Run#

To build and run the project, follow these steps:

1. Clone the repository:
   bashCopy

   git clone https://github.com/ahmmedrejowan/NumberConverter.git

2. Open the project in Android Studio.
3. Sync the project with Gradle files.
4. Connect your Android device or start an emulator.
5. Click on the "Run" button in Android Studio to build and run the app.

Release Builds#

Release signing reads from keystore.properties in the project root (gitignored), falling back to the KEYSTORE_FILE, KEYSTORE_PASSWORD, KEY_ALIAS, and KEY_PASSWORD environment variables used by CI:

storeFile=release.keystore
storePassword=...
keyAlias=...
keyPassword=...

Without either, assembleRelease still builds — it just produces an unsigned APK.

Testing#

# Run unit tests
./gradlew test

# Run instrumented tests
./gradlew connectedAndroidTest

Conversion and calculation logic is covered by unit tests across BaseConverter, the explanation generators, the repositories, the use cases, and both ViewModels.

Contributing#

Contributions are welcome! Please read CONTRIBUTING.md for guidelines.

Quick Start#

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

License#

Copyright (C) 2026 K M Rejowan Ahmmed

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

Warning This is a copyleft license. Any derivative work must also be open source under the same license.

See LICENSE for the full text.

Community#

• Discussions - Ask questions, share ideas
• Issues - Report bugs, request features
• Releases - Download latest versions

Author#

K M Rejowan Ahmmed

• GitHub: @ahmmedrejowan
• Email: kmrejowan@gmail.com

Acknowledgments#

• Jetpack Compose - Modern Android UI toolkit
• Material Design 3 - Design system
• Room - Database library
• DataStore - Preferences storage
• Koin - Dependency injection framework
• MockK - Mocking library for Kotlin
• Turbine - Testing library for Kotlin Flow
• Ubuntu - Typeface, via Google Fonts

Changelog#

v2.0.0 (2026-08-12) - Full Rewrite#

• Binary, Octal, Decimal, and Hexadecimal conversion with fractional support
• Step-by-step explanation sheets for every conversion
• Mixed-base calculator with +, −, ×, ÷ and calculation breakdowns
• Conversion history with search and bookmarks
• Material 3 design with dark mode, dynamic colors, and font size options
• Clean Architecture with MVVM, 100% Kotlin, fully offline
• Relicensed under GNU GPL v3.0

v0.1 (2024-06-25) - Initial Release#

• Single-screen View-based converter for the four number bases

See CHANGELOG.md for full version history.