The two factors: kilometres are exact, land miles are the catch
The kilometre value is exact by definition. The statute-mile value is what trips people up: a nautical mile is 15% longer than the land mile you drive in. To go the other way, divide — land miles ÷ 1.15078, or kilometres ÷ 1.852.
Nautical vs statute mile — the same "mile" is two different lengths
A land (statute) mile is 5,280 feet, an old Roman figure with no tie to the planet. A nautical mile is one minute of latitude on the globe. Read a distance off a sea or air chart as land miles and you undershoot the real distance by about 15%.
Same word, different length: the nautical mile is the longer of the two by roughly one part in seven.
Common distances and speeds
| Nautical miles | Kilometres | Statute miles |
|---|---|---|
| 1 NM | 1.852 km | 1.151 mi |
| 5 NM | 9.26 km | 5.754 mi |
| 10 NM | 18.52 km | 11.508 mi |
| 50 NM | 92.6 km | 57.539 mi |
| 100 NM | 185.2 km | 115.078 mi |
The same numbers work for speed: 20 knots is 20 NM/h, which reads across as 37.0 km/h or 23.0 mph.
Where each unit is used
- Knot. One nautical mile per hour. Ships, aircraft and marine wind reports are all in knots, never mph, so the whole system stays consistent.
- Sea and air charts. Because one nautical mile equals one minute of latitude, you can step off distance directly against the latitude scale printed on a chart's edge — no scaling.
- Land maps. Road and hiking distances stay in statute miles or kilometres. Only switch to nautical miles for water or air travel.
Common questions
Is a nautical mile longer than a regular mile?
Yes. One nautical mile is 1.15078 statute (land) miles, so it is about 15% longer. A 100 nautical mile trip is 115 land miles.
Why is a nautical mile exactly 1.852 kilometres?
It is set by international agreement to match one minute of arc of latitude on the Earth. That link to the globe is what makes it convenient for navigation, and the round metric value of 1.852 km was fixed to standardise it.
How do I convert knots to km/h and mph?
A knot is one nautical mile per hour, so multiply knots by 1.852 for km/h and by 1.15078 for mph. 20 knots is 37 km/h or 23 mph.
