A knot is one nautical mile per hour. Because a nautical mile is one minute of latitude, speed in knots maps directly onto progress along a meridian. A vessel doing 14 knots covers 14 nautical miles every hour through the water.

How is voyage time calculated?

Voyage time in hours equals distance in nautical miles divided by speed in knots. The tool then breaks that into days, hours, and minutes. For example 3360 nautical miles at 14 knots is 240 hours, which is exactly 10 days.

How do I find the speed needed to meet a deadline?

Required speed equals distance divided by the available time in hours. If you have 3360 nautical miles to cover in 9 days, that is 216 hours, so you need 3360 divided by 216, about 15.6 knots. Check that figure against the vessel's safe maximum.

Does this use speed through water or over ground?

The calculation is purely geometric, so it uses whatever speed you enter. For an accurate ETA use speed over ground, which already includes the effect of currents and leeway. Speed through the water alone will mislead the arrival time in a strong set.

What about pilotage, canals, and port time?

The tool gives steaming time only. Add allowances for pilot boarding, canal transits, slow-steaming zones, and any waiting for a berth or tide. Build a margin into the ETA so you arrive within the laycan rather than exactly on the wire.

Ship ETA / Speed / Time Calculator

Every voyage estimate comes down to one relationship between distance, speed, and time. Know any two and the third follows. This calculator solves all three cases: voyage time at a planned speed, the speed required to make a deadline, or an arrival timestamp from a departure time.

How it works

The core relationship in nautical units is distance in nautical miles, speed in knots (nautical miles per hour), and time in hours:

time (h)   = distance / speed
speed (kn) = distance / time
ETA        = departure + time(h)

A knot is one nautical mile per hour, so the arithmetic is direct: 240 nautical miles at 12 knots takes 20 hours. The tool converts the hours result into days, hours, and minutes, and in ETA mode adds the steaming time to the departure timestamp you provide.

Example and tips

A 3360-nautical-mile passage planned at 14 knots takes 240 hours — exactly 10 days. If the charterer needs the ship alongside in 9 days (216 hours), the required speed climbs to 3360 / 216 ≈ 15.6 knots; check that against the vessel’s safe and economical maximum before committing. Always use speed over ground for ETA so currents are already baked in, and add margins for pilotage, canals, and any wait for berth or tide so you land inside the laycan.