Miles to Kilometres Converter
Convert distances between miles, nautical miles, kilometres, metres, feet and yards, and speeds between mph, knots, km/h and m/s. A mile is 1.609344 km and a nautical mile 1.852 km.
- Conversion factor1 mi = 1.609344 km
- Kilometres1.609344 km
- Miles1 mi
- Nautical miles0.868976 nmi
In every unit
How it is calculated
There are two miles. The statute mile is used for road distances in the US and the UK: 5,280 feet or 1,760 yards, which with the international yard of 1959 (0.9144 m) is exactly 1,609.344 metres (NIST; UK Weights and Measures Act 1985, Schedule 1). The nautical mile is used at sea and in the air; it was chosen because it subtends about one minute of arc at the centre of the Earth, and it has been exactly 1,852 metres since the First International Extraordinary Hydrographic Conference of 1929 (SI Brochure). For speed, a knot is one nautical mile an hour and mph one statute mile an hour. These definitions are exact, so the conversions are too.
km = mi × 1.609344 · km = nmi × 1.852 · m/s = km/h ÷ 3.6- Miles to kilometres: miles × 1.609344 (kilometres to miles: km ÷ 1.609344 ≈ km × 0.621371).
- Nautical miles to kilometres: nautical miles × 1.852.
- Speeds use the same factors: mph × 1.609344 = km/h, knots × 1.852 = km/h.
- Divide km/h by 3.6 for m/s (an hour is 3,600 seconds and a kilometre 1,000 m).
Example
100 miles = 100 × 1.609344 ≈ 160.93 km. 50 nautical miles = 50 × 1.852 = 92.6 km. 120 km/h = 120 ÷ 1.609344 ≈ 74.56 mph. 10 knots = 18.52 km/h. 42.195 km is about 26.22 miles.
Frequently asked questions
How many kilometres is a mile?
A statute mile is 1.609344 km, roughly 1.6 km. A nautical mile is 1.852 km. A plain “mile” means the statute mile on land and the nautical mile at sea and in the air.
How many miles is a kilometre?
1 ÷ 1.609344 ≈ 0.621371 miles, and 1 ÷ 1.852 ≈ 0.539957 nautical miles.
What is a knot in km/h?
A knot is one nautical mile an hour: 1 knot = 1.852 km/h ≈ 0.514 m/s. A ship at 20 knots covers 37.04 km an hour.
What is 70 mph in km/h?
70 × 1.609344 ≈ 112.65 km/h. 70 mph is the UK motorway speed limit for cars (gov.uk), about 113 km/h.
Why is a nautical mile 1,852 metres?
According to the BIPM, the nautical mile was chosen because one nautical mile on the Earth’s surface subtends about one minute of arc (1/60 of a degree) at the Earth’s centre; since latitude and longitude are measured in degrees and minutes, a minute of latitude on a chart is about one nautical mile. Its value, exactly 1,852 metres, was adopted as the “international nautical mile” by the First International Extraordinary Hydrographic Conference, Monaco, 1929.
Source
- NIST: Revised unit conversion factors (mile = 5,280 ft = 1,609.344 m)
- UK Weights and Measures Act 1985, Schedule 1 Part VI (mile = 1,760 yards, yard = 0.9144 m)
- BIPM, The SI Brochure (9th ed.), Table 8 and note (k): nautical mile = 1,852 m, knot; 1929 Hydrographic Conference
- BIPM, The SI Brochure (8th ed., 2006), Table 8 note (d): the nautical mile and one minute of arc
- GOV.UK: Speed limits (cars on motorways 70 mph / 112 km/h)
- NIST SP 811, Appendix B.9: Conversion factors (mile, nautical mile, knot)
- NIST: The US survey foot and the international foot (1959)