Miles per Hour to Knots

Miles per hour and knots

A mile per hour is one international mile per hour: exactly 0.44704 m/s, or 1.609344 km/h. Speed limits and speedometers in the US and UK, and pitch speeds in baseball, use mph.

The knot is one nautical mile per hour: exactly 1.852 km/h. Ships, aircraft, and wind speeds in aviation and marine forecasts are measured in knots.

Worked example

Convert 100 mph: 100 × 0.8689762419 = 86.89762419, so 100 miles per hour is 86.89762419 knots. Likewise 200 mph = 173.7952484 kn.

Estimating in your head

Multiply by 0.87 for a quick figure; it is off by about 0.1%. For 100 mph that gives 87 kn, against 86.8976 exactly.

Going the other way

To convert knots to miles per hour, divide by 0.8689762419 (or multiply by 1.15077944802). The swap button between the boxes opens that page.

kn = mph × 0.8689762419

1 mph = 0.44704 m/s and 1 kn = ≈ 0.5144444444 m/s, both by definition, so the factor is their ratio: 0.8689762419 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.