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Knots to MPH Converter

Enter a speed in knots to convert to mph and km/h.

How it is calculated

The tool converts a speed in knots with two multipliers: mph = knots × 1.15077945 and km/h = knots × 1.852. A knot is one nautical mile per hour, and a nautical mile is exactly 1,852 m, so the km/h factor is exact. The mph factor is the nautical mile divided by the statute mile (1,609.344 m). Both answers are rounded to two decimals. The tool accepts any number, including 0 and negatives, without limits. It converts a speed only; a wind or boat speed in knots is not changed by the conversion, only its unit.

Worked example

A forecast gives a wind of 25 knots. Miles per hour: 25 × 1.15077945 = 28.769, shown as 28.77 mph. Kilometres per hour: 25 × 1.852 = 46.30 km/h. A quick check: the km/h figure is a little under double the knot value, and the mph figure is about 15 percent above it.

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Common mistakes

  • Treating knots as equal to mph; the knot is about 15 percent faster, so 25 knots is almost 29 mph.
  • Confusing a nautical mile (1,852 m) with a statute mile (1,609.344 m) when quoting a distance travelled.
  • Writing "knots per hour", which is a rate of acceleration; a knot is already a speed, a nautical mile per hour.
  • Rounding the factor to 1.15 for long conversions, where the error grows with the speed.

About this calculator

A knot is one nautical mile per hour, and a nautical mile (1,852 metres exactly, by international definition) is the length of one minute of arc along a great circle of the Earth — which is why sailors and aviators use it instead of statute miles: it ties speed directly to how far a vessel or aircraft is moving across the globe's latitude/longitude grid.

This calculator converts a speed in knots to miles per hour (× 1.15078) and kilometres per hour (× 1.852). It's essential wherever knots are the native unit — maritime navigation, aviation airspeed and wind readings, and marine weather forecasts — but a more familiar unit is needed for planning or comparison.

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Comments (1)

  • Editorial team

    On the water, remember that this only changes the unit of a speed you already have. A boat reading 6 knots through the water while pushing against a 2 knot current is making good only 4 knots over the ground, so convert the figure that matches the question you are asking. For a quick mental check, add about 15 percent to the knots to get mph. Do you mostly convert boat speed, wind forecasts or aircraft airspeed?

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