Knots to Miles per Hour Converter

A knot is one nautical mile per hour. A nautical mile is 1,852 meters, longer than the 1,609.344-meter mile used on roads, so the same speed is always a smaller number in knots than in mph. The converter defines a knot as exactly 1852 m per 3600 s, about 0.514444 m/s, and a mile per hour as exactly 0.44704 m/s, which gives 1 kn = 1.1508 mph.

Sailors and pilots stick with knots because nautical charts measure distance in nautical miles. A speed in knots then tells you straight away how long a leg takes: at 6 knots, a 30-nautical-mile passage is 5 hours. Convert to mph only when you need to compare with something measured on land, such as a road journey or a land-based weather report.

Multiplying knots by 1.15, which is the same as adding 15%, lands within 0.068% of the converter at every speed. The percentage never changes, so the miss in mph grows with speed:

Even at 450 knots the shortcut is only 0.35 mph short. Use it for a feel of the speed; use the converter for anything you write down in a log or a report.

• Wind. Marine forecasts usually give wind in knots. A 25-knot wind is 28.7695 mph. Switch the To list to kilometers per hour and 10 knots reads 18.52 km/h.
• Boats. A sailboat logging 6 knots is moving at about 6.9 mph. For a boat, one decimal place is plenty.
• Aircraft. 450 knots converts to 517.85 mph. The converter only changes the unit: if the figure is airspeed, the answer is still airspeed. Wind changes the speed over the ground, and no unit conversion accounts for that.

Press the swap button and the converter divides instead: 1 mph = 0.86898 kn. In your head, take off 13%. For 10 mph that gives 8.7 knots against the exact 8.6898, an error of about 0.12%. This direction comes up when a land forecast in mph needs to go into a sailing plan written in knots.