How to use the nautical unit converter
Type a value into any box and every other unit in that group updates straight away. There are three groups: speed (knots, km/h, mph and m/s), distance (nautical miles, kilometres, statute miles and cables) and depth or length (metres, feet and fathoms).
The conversion factors
1 knot = 1 nautical mile per hour = 1.852 km/h = 1.15078 mph = 0.51444 m/s
1 nautical mile = 1,852 m = 1.852 km = 1.15078 statute miles = 10 cables
1 fathom = 6 feet = 1.8288 m
1 foot = 0.3048 m
The international nautical mile has been exactly 1,852 metres since 1929. It was chosen because one nautical mile is very close to one minute of latitude, so distances can be measured straight off the latitude scale of a chart. That is why navigators still use nautical miles and knots rather than kilometres and km/h.
Where the names come from
- Knot: sailors once measured speed by paying out a log line with knots tied at regular intervals and counting how many ran out in a set time.
- Fathom: originally the span of a man's outstretched arms. It is still used for depths on older charts and for anchor chain.
- Cable: in navigation, a tenth of a nautical mile (185.2 m), handy for short distances such as passing distances and anchorage positions.
Quick conversions
| Nautical miles | Kilometres | Statute miles |
|---|---|---|
| 1 nm | 1.9 km | 1.2 mi |
| 10 nm | 18.5 km | 11.5 mi |
| 50 nm | 92.6 km | 57.5 mi |
| 100 nm | 185.2 km | 115.1 mi |
| 500 nm | 926 km | 575.4 mi |
| 1,000 nm | 1,852 km | 1,150.8 mi |
| 3,000 nm | 5,556 km | 3,452.3 mi |
Need the time for a passage rather than a conversion? Use the voyage ETA calculator. For under-keel clearance in metres, see the squat calculator.