What is a Nautical Mile?

The nautical mile equals exactly 1,852 meters and is the international standard distance unit for marine navigation, aviation, and polar geography. It was originally defined as one minute of arc along a meridian — meaning 60 nautical miles equal one degree of latitude. This relationship makes the nautical mile uniquely useful for charts: a navigator can read distance directly off the latitude scale of any map. Adopted internationally in 1929, the nautical mile is used by virtually all maritime nations and in international aviation regulations. The related speed unit is the knot (1 nautical mile per hour). The nautical mile is roughly 1.151 statute miles or 1.852 km. Distinct from the older British nautical mile (6,080 ft) and the US nautical mile (6,080.20 ft), the international nautical mile is now standard worldwide.

Visual reference for how the nautical mile relates to other length units. Each row links to the full converter for that pair.

See all 15 length units in matrix view →

• Marine navigation and nautical charts
• Commercial and military aviation distances
• International maritime law (territorial waters = 12 nmi)

• ✓1 nautical mile = 1.852 km = 1.151 statute miles.
• ✓A knot (1 nmi/h) equals 1.852 km/h — remember this for weather and sailing reports.
• ✓Latitude is measured in degrees and minutes; one minute of latitude equals exactly one nautical mile.

• ✗Confusing nautical miles with statute miles — the 15% difference matters in flight planning.
• ✗Reading knots as km/h on weather reports — a 40-knot wind is 74 km/h, not 40.
• ✗Using nautical miles on land — outside navigation contexts, use kilometres or statute miles.