Maritime Master - CalcDeck

CalcDeck is the complete calculation toolkit for life at sea. It brings 88 professional maritime calculators into one beautifully designed iOS app, covering navigation, celestial observation, tides, stability and cargo, weather, engineering, safety, commercial voyage work, yacht and small craft performance, regulatory compliance and unit conversion.

Whether you are a Master Mariner, deck officer, marine engineer, maritime cadet, yacht skipper or weekend sailor, CalcDeck replaces a shelf of reference books, a scratch pad and a pocket full of single-purpose apps. Every formula is cited with its textbook or IMO source, so you can verify the working and trust the result.

CalcDeck is built by Maritime Master, the team behind COLREG Master, Nav Lights and IALA Buoyage, and is engineered to the same professional standard trusted by cadets and officers worldwide.

What is inside

Navigation (12 calculators): great-circle and rhumb-line distance, course to steer, ETA, set and drift, three-point fix, running fix, dead reckoning, cross-track error, waypoint bearing, speed-time-distance, departure and DMP, Mercator sailing.

Celestial (8 calculators): sight reduction, meridian passage, altitude corrections, sunrise, sunset and twilight times, Polaris latitude, compass error by amplitude, azimuth of the sun, and chronometer error.

Tidal (6 calculators): tidal height by the rule of twelfths, secondary port corrections, tidal streams, height at a given time, time at a given height, and clearance under bridges.

Stability and Cargo (9 calculators): GM and list, trim and draft survey, free surface correction, deadweight and displacement, cargo load, block coefficient, TPC and MCTC, and final draft after loading.

Weather (6 calculators): true wind, apparent wind, relative humidity, dew point, Beaufort scale conversion, and barometric trend.

Engineering (10 calculators): fuel consumption and ROB, daily fuel burn, propeller slip, shaft power, specific fuel consumption, bunker density correction, trim tank transfer, admiralty coefficient, engine load, and voyage fuel planning.

Safety (5 calculators): distance off by vertical sextant angle, horizon distance, dipping range, turning circle, and stopping distance.

Yacht and Small Craft (5 calculators): hull speed, sail area to displacement, displacement to length, capsize screening, and ballast ratio.

Commercial and Voyage (6 calculators): voyage cost, laytime, demurrage, freight rate per tonne, charter economics, and port disbursements.

Regulations and Compliance (6 calculators): MARPOL discharge limits, SOLAS LSA requirements, STCW rest-hour compliance, load line zones, ballast water exchange, and garbage record categorisation.

Unit Converters (12 calculators, all free): distance, speed, temperature, pressure, volume, mass, area, power, energy, angle, time and fuel. Every unit a mariner needs.

Why CalcDeck

CalcDeck works fully offline, so there is no signal, no signup and no interruption when you need an answer at sea. It is a native SwiftUI app designed for iPhone and iPad on iOS 17 and later, with a clean navy and gold Maritime Master design, dark mode support, favourites, and a Calc Pad that lets you pin your most-used tools for instant access on watch. There are no advertisements, no tracking and no subscriptions.

Free and Pro

You can try CalcDeck at no cost. All 12 unit converters and a selection of essential calculators in every professional category are included free. Unlock the full 85-calculator suite with a single one-time in-app purchase that is yours forever across all your devices.

Who it is for

CalcDeck is used by deck officers and Masters on coastal and ocean passages, by marine engineers calculating fuel, power and performance, by maritime cadets preparing for OOW, Chief Mate and Master examinations, by yacht skippers and RYA students, by cruising sailors, by pilots, harbourmasters and port operations staff, and by naval architects, surveyors and marine consultants.