Kilometers per Hour to Knots Converter (km/h to kn)

Weather apps and TV forecasts in most countries give wind in kilometers per hour, but sailing guides, harbor rules and aviation limits are written in knots. Converting divides by 1.852, because a knot is exactly 1.852 km/h, so the knot figure always comes out a little more than half the km/h figure.

The conversion is most useful for deciding whether a forecast is within your limits: a dinghy sailor whose comfort zone is set in knots needs to read a 40 km/h gust as about 21.6 kn. The table below lists the Hong Kong Observatory's tropical cyclone classes, which are published in km/h, beside the knot values used by marine and aviation forecasts.

How to use this tool

1. Type a value in the Kilometer per Hour box to see it in knots, or type in the Knot box to convert the other way.
2. Press ⇄ to swap the two units, or Load example for a typical value.
3. Check the charts below for common values; for other units, open the Speed converter.

Formula

Knot (kn) = Kilometer per Hour (km/h) × 0.539956803456

Kilometer per Hour (km/h) = Knot (kn) × 1.852

Both factors come from exact definitions: 1 knot = 1.852 kilometers per hour and 1 kilometer per hour = 0.539956803456 knots (shown to 12 significant digits).

Example

Two conversions worked with the same factors the converter uses:

40 km/h × 0.539956803456 ≈ 21.5983 kn

15 kn × 1.852 = 27.78 km/h

Kilometer per Hour to Knot chart

Common values from kilometers per hour to knots, rounded to four decimal places.

Knot to Kilometer per Hour chart

The reverse direction for values people often look up.

Tropical cyclone classes published in km/h

Quick mental estimate

Halve the km/h and add 8% of that half: 100 km/h → 50 + 4 = 54 kn, against an exact 53.996 kn. The method multiplies by 0.54, less than 0.01% off the true factor, so it is as good as exact for wind and boat speeds.

Use the converter or the charts when the exact figure matters.

The two units

Kilometer per Hour (km/h): The kilometre per hour is the speed unit on road signs and speedometers in most of the world. Because 1 km is 1000 m and 1 hour is 3600 s, 1 km/h is exactly 5/18 m/s (about 0.2778 m/s).

Knot (kn): A knot is one nautical mile per hour. The international nautical mile is exactly 1852 m, so 1 knot is 1.852 km/h (about 0.5144 m/s); it is the standard speed unit at sea, in aviation and in marine weather.