🧭 Sailing Distance Calculator
Enter two waypoints and your average boat speed to get the great-circle passage distance in nautical miles, kilometres, and statute miles, plus an estimated passage time.
🌊 Two Waypoints, One Passage
What is a Sailing Distance Calculator?
It measures how far it is between two points on the water and how long the trip might take. Give it the latitude and longitude of a start and a destination and it applies the Haversine formula to return the great-circle distance — the shortest arc over the globe — in nautical miles, kilometres, and statute miles. Add your average boat speed and it divides through to estimate the passage time in hours and minutes.
Use it to scope out a day sail or a longer passage, compare route options, and sanity-check whether you'll make landfall in daylight. Remember it's the straight-line minimum: real passages tack, dodge hazards, and follow the wind, so add distance and time, and plan properly with charts and official sources.
❓ Frequently Asked Questions
How is the sailing distance calculated?
It uses the Haversine formula to find the great-circle distance — the shortest path over the curved surface of the Earth — between two latitude/longitude waypoints, using Earth's mean radius. The result is reported in nautical miles (the sailor's unit), kilometres, and statute miles, and then divided by your boat speed to estimate passage time.
Why nautical miles instead of statute miles?
One nautical mile is one minute of latitude, so it maps directly onto a chart and to speed in knots (one knot is one nautical mile per hour). That's why passage planning, chart distances, and boat speeds are all in nautical miles. This calculator shows nautical miles first and adds kilometres and statute miles for reference.
Will my actual passage be this distance?
No — this is the straight great-circle distance, and a real passage is almost always longer. Sailing to windward you have to tack, and you'll route around headlands, shoals, traffic separation schemes, and foul weather. Treat the figure as the irreducible minimum and add a generous margin for the course you'll actually sail.
How reliable is the passage time estimate?
It's only as good as the average boat speed you enter, and boat speed over a passage varies enormously with wind, current, and sea state. Use a realistic average speed of advance rather than your best boat speed, and remember that a foul tide or a calm can add hours. It's a planning estimate — always allow contingency for arriving in daylight and on a fair tide.