CaptainCalc — Offline bridge tools for working mariners

Android app for bridge officers, chief officers, and ship masters who need voyage planning, draft survey, stability, celestial navigation, cargo tools, and COLREG/IALA references available at sea.

Feedback

Install from Google Play. Core calculation tools are built to work without internet at sea.

Offline-first No dependency on internet at sea.

Fast input DD/DMS/DDM-friendly coordinates and quick forms.

Almanac-grade SOFA-based ephemeris + almanac snapshot golden tests.

Rules reference COLREG + diagrams + sound signals.

Made for bridge teams For officers, masters, cadets, and working mariners on merchant vessels.

Solves daily bridge problems Plan routes, check cargo and stability figures, reduce sights, and keep regulation references close.

Offline when it matters Core tools run locally, so weak signal at sea does not block operational checks.

Technical Highlights & Accuracy

Built on a highly deterministic mathematical core with >55 FPS performance and an astonishing 523+ golden regression test suite to ensure consistent, reliable results.

Voyage & Routing

Büyük Daire (Haversine) and Rhumb Line (Loxodromic) precision down to ±0.01 NM. Includes live GPS tracking, waypoint management, and XTE warnings.

±0.01 NM Cross Track Error Live GPS Templates

Celestial Motor (SOFA + JPL)

Unprecedented accuracy using IAU SOFA and NASA JPL DE440 ephemeris. Tracks 57 navigation stars with finals.a DUT1 microsecond-level corrections.

SOFA Engine JPL DE440 57 Stars finals.a (DUT1)

Deterministic Stability

Calculates GM, KG, and GZ curves with ±0.001 m precision. FSM integration and full draft survey workflows built into native modules.

±0.001 m Precision GZ Curves Draft Survey Hold Capacity

Architecture & Rules

Fully offline 14-module architecture adhering to COLREG (38 rules), SOLAS, IALA, and IAMSAR references natively inside the app.

Offline-First COLREG SOLAS & IALA

Uncompromising Testing & Validation

CaptainCalc operates as a trusted truth source. Over 523+ Golden Regression Tests validating everything against strict tolerances, achieving >80% coverage on the core-math module.

Professional Decision Support

While it rivals or exceeds the accuracy of USNO API and nautical tables, always verify critical cargo/stability decisions with the vessel's approved booklets/systems.

Application Preview

Native UI components built with Compose, optimized for performance and offline reliability.

FAQ

No. It is a decision support tool. Always verify with approved booklets systems.

By utilizing JPL DE440 and IAU SOFA, CaptainCalc tracks UT1-UTC (DUT1) accurately, outperforming standard almanac APIs with ±0.001° internal precision.

Merchant vessels (container, tanker, bulk, general cargo). Adapted via intricate vessel profiles, tank calibrations, and float profiles.

Yes! It has an independent SQLite (Room) Database and fully offline core determinism.