Sailing Distance, Speed and Passage Time Calculator
Passage details
Result
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Distance, speed, and time formulas
The calculator converts the inputs to nautical miles, knots, and hours before solving the selected value.
Passage time = distance ÷ average speed
Distance = average speed × passage time
Average speed = distance ÷ passage time
Because one knot is one nautical mile per hour, 120 nautical miles at an average of 6 knots takes 20 hours.
How to use this calculator
- Choose whether to calculate passage time, sailing distance, or required average speed.
- Enter the two known values and select their units.
- Use route distance from appropriate navigation information rather than a visual straight-line guess.
- For arrival estimates, use a conservative average speed over ground that reflects expected conditions and maneuvers.
- Optionally enter a local departure time, then review the result alongside a complete passage plan.
Example sailing passage calculation
A route measures 120 nautical miles and the boat is expected to average 6 knots over the ground.
120 nmi ÷ 6 kn = 20 hours
If departure is at 08:00 local time, the arithmetic arrival is 04:00 the following day. That estimate assumes the 6-knot average is maintained across the whole route, including any slower legs.
Choosing a realistic average speed
For an ETA, average speed should describe progress over the ground along the planned route. A brief instrument reading, theoretical hull speed, or best speed on one point of sail is usually too optimistic.
- Allow for tacking or gybing by using the actual route length.
- Consider forecast current, wind, sea state, sail changes, traffic, and restricted waters.
- Include expected slower sections in the average rather than adding them invisibly after the calculation.
- Recalculate underway using observed progress and current official information.
Frequently asked questions
How do you calculate sailing passage time?
Divide route distance by average speed over ground. At 6 knots, a 120-nautical-mile route takes 20 hours at a constant average speed.
How far can a sailboat travel at 6 knots in 24 hours?
The arithmetic result is 144 nautical miles. Actual progress can differ because of the sailed route, currents, wind, waves, sail changes, traffic, and other delays.
Is one knot the same as one nautical mile per hour?
Yes. One knot is one nautical mile per hour. One international nautical mile is exactly 1.852 kilometers, so one knot equals exactly 1.852 km/h.
Should I enter speed through the water or speed over ground?
Use a realistic average speed over ground when estimating arrival time along a charted route. Speed through the water does not include the current's effect on progress over the ground.
Does this calculator account for tides, currents, wind, or tacking?
No. Include their expected combined effect in the average speed and route distance you enter. Do not treat the output as weather routing or a complete passage plan.
Why can actual arrival time differ from the result?
The result assumes one constant average. Maneuvers, course changes, current, changing wind, sea state, traffic, equipment issues, rest decisions, and safety actions can all alter progress.
Are my route and departure inputs uploaded or tracked?
No. Calculations run locally in the browser, and this tool does not send, store, or attach entered values to analytics events.
Assumptions and safety limits
- The model treats distance and average speed as constant scalar values. It does not calculate bearings, vectors, set and drift, leeway, tacking angles, great-circle routes, or changing leg speeds.
- The optional arrival time adds elapsed seconds to the local departure time. Device time-zone settings and daylight-saving transitions determine the displayed local time.
- A route measured in nautical miles and speed entered in knots fit the formula directly. Other units are converted using international definitions.
- Very precise results can imply false certainty, so displayed results are rounded even though calculations use unrounded values.
Safety disclaimer: This educational arithmetic tool does not replace current charts, notices, forecasts, tide and current data, vessel guidance, legal requirements, or the judgment of the skipper and crew.
Methodology and sources
Last reviewed: August 1, 2026. The calculations use direct time-rate-distance relationships. Marine units and passage-planning context were checked against: