Nitrox/Trimix MOD Calculator
A mobile app for recreational and technical divers to calculate MOD, EAD and END for Nitrox and Trimix. Built with React Native and available on Android.
Dive-planning calculations are simple in principle, but they need to be fast, clear and dependable when used in practice. I built this app as a focused tool for recreational and technical divers to calculate MOD, EAD and END for Nitrox and Trimix mixtures without relying on an internet connection.
The project also gave me an opportunity to build and release a complete mobile product with React Native and Expo, from calculation logic and persistent storage through interface design, testing and store deployment.
ENGINEERING APPROACH
Built for clarity and reliability
The interface is intentionally simple, while the underlying calculation logic is kept modular and independent from the presentation layer. The result is a fast, offline-first tool that remains easy to test, maintain and use in real diving workflows.
Offline by Design
Core calculations, preferences and history remain available without an account or network connection.
Reliable Calculation Layer
MOD, EAD, END and validation are handled separately from the UI, keeping critical gas-planning logic testable and predictable.
Cross-Platform by Default
React Native and Expo provide a shared TypeScript codebase across mobile platforms.
Project Gallery
Gallery Subtitle
05 Screens
Screen 01
Gas Calculator
The primary interface keeps the most important result — Maximum Operating Depth — visually dominant while allowing divers to quickly adjust gas composition, ppO₂ and unit preferences.
Screen 02
Tank Label
Calculated gas data can be turned into a simple tank label containing the diver's name, date, oxygen percentage and MOD, connecting the digital calculation with a familiar real-world diving workflow.
Screen 03
Calculation History
Previous calculations can be stored locally and remain available offline, making it easy to revisit recently used Nitrox and Trimix mixtures without entering them again.
Screen 04
Settings
Settings provide lightweight control over the diver profile, preferred units and stored calculation history, with preferences persisted locally between sessions.
Screen 05
Learn
A built-in reference section explains essential concepts behind gas planning, including Dalton's Law, oxygen exposure and inert-gas behaviour, with content bundled directly into the app for offline access.