True vs ETA Calculator

The wind you feel on a moving boat isn't the real wind. True-Wind Calculator turns the apparent wind you measure into the true wind you need — in two taps, no wind instruments required. In use since 2013, completely rebuilt in 2026. HOW IT WORKS Enter boat speed, apparent wind speed, apparent wind angle and heading. The app does exact vector math — no lookup tables, no approximations — and gives you true wind speed and true wind direction instantly. Boat speed and heading can be filled automatically from GPS and compass with one tap. FREE • True wind speed, direction and angle — unlimited calculations • One-tap GPS fill for boat speed and heading • The formula explained, so you can trust the numbers • Works completely offline — no account, no ads, no tracking PRO (one-time purchase, no subscription) • Performance — live VMG, target boat speed, % of target VMG and point of sail, driven by your boat's polar • Tactics — tack preview, windward-mark laylines, and whether you can lay the mark • Boat polars — pick a preset or build your own in the editor • Compass rose view — heading, apparent and true wind on one dial • Calculation history — every result logged with its inputs • All speed units — knots, m/s, km/h, mph Bought the app back when it was paid? Pro is already yours — it unlocks automatically. PRIVACY Everything stays on your device. Location is read only to fill the input fields and never leaves your phone. No analytics, no third-party SDKs.

Calculate ETA and required speed quickly with a practical maritime voyage planning tool built for seafarers. ETA Calculator helps masters, deck officers, bridge watchkeepers, cadets, and other maritime professionals manage voyage timing with fast and straightforward calculations. Whether you need to estimate when your vessel will arrive or determine the speed required to meet a planned arrival time, the app gives you the result in seconds. TWO ESSENTIAL MARITIME CALCULATIONS • Estimated Time of Arrival (ETA) Enter the remaining distance and vessel speed to calculate the expected arrival time. • Required Speed Enter the remaining distance and your desired arrival time to calculate the speed required to reach the destination on schedule. SAVE YOUR CALCULATIONS Save calculation results for later reference, making it easier to keep important voyage timing information available when you need it. BUILT FOR USE AT SEA • Works completely offline • Fast and simple data entry • Clear, easy-to-read calculation results • Save calculation results • 24-hour time format • Light and dark themes • Designed for quick use on the bridge • Suitable for vessels of any type and size USEFUL FOR • Voyage and passage planning • ETA monitoring during a voyage • Speed planning • Bridge watch operations • Time-critical maritime operations • Maritime training and simulation exercises ETA Calculator is focused on what maritime professionals need most: fast calculations, clear results, reliable offline access, and a simple workflow without unnecessary complexity. Plan your voyage. Check your ETA. Calculate the required speed. Save the result and keep your voyage timing under control. ETA Calculator is intended as a calculation and planning aid. Navigational decisions should always follow applicable procedures, official voyage planning requirements, and professional judgment.