Boat Speed Calculator
Enter the distance you traveled and how long it took to find your boat’s speed in knots, mph, and km/h.
How boat speed is measured
Marine speed is traditionally measured in knots, which is nautical miles per hour. One nautical mile (1.852 km) is based on one minute of latitude, which is why it differs slightly from the statute mile used on land.
The formula
Speed is simply distance divided by time: Speed = Distance ÷ Time. This calculator takes the nautical-mile distance you traveled and the time it took, then converts the result into knots, miles per hour, and kilometers per hour so you can compare it to GPS or land-speed readouts.
This is your average speed over ground for the trip — actual speed through water can vary with current, wind, and throttle changes along the way. Use it for general trip planning and educational purposes.