Nautical Speed Converter
Convert between knots, miles per hour, kilometers per hour, and meters per second for nautical and marine speed.
Type in any field.
Type in any field — the others update instantly.
Nautical speed is most commonly measured in knots (kn), which is the standard unit used by mariners, pilots, and meteorologists worldwide. One knot equals one nautical mile per hour.
What is a nautical mile? A nautical mile is based on the geometry of the Earth. It equals exactly 1,852 meters (about 1.151 statute miles or 6,076 feet). One nautical mile corresponds to one minute of latitude, which makes it extremely practical for navigation using charts.
Conversion factors using meters per second as the base:
- 1 knot = 0.514444 m/s (exactly 1852/3600)
- 1 mile per hour (mph) = 0.44704 m/s
- 1 kilometer per hour (km/h) = 0.277778 m/s (exactly 1/3.6)
- 1 meter per second (m/s) = 1 m/s (base unit)
Quick mental approximations:
- Knots to mph: multiply by 1.15 (or add about 15%)
- Knots to km/h: multiply by 1.85 (or nearly double minus 15%)
- Mph to km/h: multiply by 1.6
Beaufort Scale reference (wind speed):
| Beaufort | Knots | km/h | mph | Description |
|---|---|---|---|---|
| 0 | less than 1 | less than 2 | less than 1 | Calm |
| 3 | 7-10 | 12-19 | 8-12 | Gentle breeze |
| 5 | 17-21 | 29-38 | 19-24 | Fresh breeze |
| 7 | 28-33 | 50-61 | 32-38 | Near gale |
| 10 | 48-55 | 89-102 | 55-63 | Storm |
| 12 | 64+ | 118+ | 73+ | Hurricane force |
Common marine speed references:
- A typical sailboat cruises at 5-8 knots (5.8-9.2 mph).
- A large cargo ship travels at about 12-16 knots (14-18 mph).
- A modern cruise ship cruises at 20-24 knots (23-28 mph).
- A fast naval destroyer can exceed 30 knots (35 mph).
- The fastest speedboats can reach over 50 knots (58 mph).
Why knots instead of mph? Knots are tied directly to the coordinate system used for global navigation. Since one knot equals one nautical mile per hour, and one nautical mile equals one minute of latitude, speed in knots translates directly to distance on a nautical chart. This makes plotting courses and calculating arrival times much simpler for navigators.