The unit of distance at sea, exactly 1,852 metres, originally one minute of latitude.
A nautical mile (nm, NM or M) is exactly 1,852 metres, about 1.15 land miles. It was originally defined as one minute of arc of latitude (1/60 of a degree along a meridian), and that link is what makes it so practical at sea.
Measuring on the chart
Because one minute of latitude is one nautical mile, the latitude scale on the side of every chart doubles as a distance scale. Take the distance with the dividers and read it off the side scale, level with where you're measuring. Never use the longitude scale at the top or bottom: minutes of longitude get shorter toward the poles.
Conversions
| Metres | Kilometres | Statute miles | |
|---|---|---|---|
| 1 nm | 1,852 | 1.852 | 1.151 |
| 0.1 nm (1 cable) | 185.2 | 0.185 | 0.115 |
Sea miles
Distance sailed is counted in nautical miles, in the logbook, in passage planning and as sea miles, the record of experience many licences and charter companies ask for. Speed at sea follows from it: one nautical mile per hour is one knot. In Manta, tours and seasons add up the miles you've sailed.
Manta does this for you
Track your sailing cruises and seasons
Group trips into a cruise, see its days at a glance, and follow your season's miles and records.
