Knots to MPH: Miles per Hour Converter
Marine and aviation speeds, with the Beaufort wind scale alongside, since most people looking this up are reading a forecast.
Enter a number.
The formula
mph = knots × 1.15077945 (rounded)
The international nautical mile is defined as exactly 1,852 meters, so the km/h relationship is exact. The mph figure is a rounded value derived from it.
Knots, mph and the Beaufort scale
| Knots | mph | km/h | Beaufort description |
|---|---|---|---|
| 1 kn | 1.2 | 1.9 | Light air |
| 4 kn | 4.6 | 7.4 | Light breeze |
| 7 kn | 8.1 | 13.0 | Gentle breeze |
| 11 kn | 12.7 | 20.4 | Moderate breeze |
| 17 kn | 19.6 | 31.5 | Fresh breeze |
| 22 kn | 25.3 | 40.7 | Strong breeze |
| 28 kn | 32.2 | 51.9 | Near gale |
| 34 kn | 39.1 | 63.0 | Gale |
| 41 kn | 47.2 | 75.9 | Strong gale |
| 48 kn | 55.2 | 88.9 | Storm |
| 56 kn | 64.4 | 103.7 | Violent storm |
| 64 kn | 73.6 | 118.5 | Hurricane force |
Beaufort force boundaries are given in knots by convention. The descriptions are the standard scale wording. This table is for reading a forecast, not for making an operational decision: for anything at sea or in the air, use the official forecast and the guidance that applies to your vessel or aircraft.
Why a nautical mile isn't a statute mile
A nautical mile is one minute of latitude, roughly 1,852 meters, against 1,609 meters for a statute mile. That definition is the whole point: a speed in knots translates directly into how fast your latitude is changing, which is what matters when navigating by chart.
Aviation adds a further wrinkle. Indicated, true and ground speeds are different quantities, and converting the unit doesn't convert between them.
Common questions
What is 20 knots in mph?
20 knots is 23.0 miles per hour, or 37.0 kilometers per hour. A knot is one nautical mile per hour, and the nautical mile is exactly 1,852 meters, so a knot is always slightly faster than a mile per hour.
Is a knot exactly 1.852 km/h?
Yes. A knot is one nautical mile per hour, and the international nautical mile is defined as exactly 1,852 meters.
Why do ships and aircraft use knots at all?
Because a nautical mile is one minute of latitude, so speed in knots maps directly onto position on a chart. That relationship is lost if you use statute miles.
What wind speed is a gale?
On the Beaufort scale, force 8 begins at 34 knots, which is 39 mph or 63 km/h.
Related converters and guides
Sources
- Marine forecasts glossary. UK Met Office. Source for the Beaufort thresholds used above: gale is force 8 at 34 to 40 knots, storm is force 10 at 48 to 55 knots, and hurricane force is force 12 at 64 knots or more. The Met Office notes the term is "hurricane force"; "hurricane" alone means a tropical cyclone.
- NIST Guide to the SI, Appendix B: Conversion Factors. National Institute of Standards and Technology. Source for every conversion factor on this page, and for which factors are exact rather than rounded.