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| km | miles |
|---|---|
| 1 | 0.621 |
| 5 | 3.107 |
| 10 | 6.214 |
| 21.0975 | 13.109 |
| 42.195 | 26.219 |
| 50 | 31.069 |
| 100 | 62.137 |
The exact definition
The international mile is exactly 1,609.344 m, so kilometers ÷ 1.609344 = miles, and miles × 1.609344 = kilometers. One kilometer is about 0.6214 miles.
Mental math shortcuts
- km to miles: multiply by 6 and divide by 10, then add a bit. 50 km → 30, plus a little → 31 mi (exact 31.07).
- miles to km: multiply by 1.6. 20 mi → 32 km (exact 32.19).
- Fibonacci trick: consecutive Fibonacci numbers are close to the ratio: 5 mi ≈ 8 km, 8 mi ≈ 13 km, 13 mi ≈ 21 km.
Race distances
| Race | Kilometers | Miles |
|---|---|---|
| 5K | 5 | 3.11 |
| 10K | 10 | 6.21 |
| 15K | 15 | 9.32 |
| Half marathon | 21.0975 | 13.11 |
| Marathon | 42.195 | 26.22 |
| 50K ultra | 50 | 31.07 |
Speed: km/h to mph
| km/h | mph |
|---|---|
| 30 | 18.6 |
| 50 | 31.1 |
| 60 | 37.3 |
| 80 | 49.7 |
| 100 | 62.1 |
| 110 | 68.4 |
| 120 | 74.6 |
| 130 | 80.8 |
Road signs in most countries use km/h; the US and UK use mph. 100 km/h is just over 62 mph.
Nautical miles are different
At sea and in aviation, a nautical mile is exactly 1,852 m (1.151 statute miles), and speed is in knots (nautical miles per hour).
The exact factor
One mile is exactly 1.609344 kilometres, so 1 km = 0.621371 miles. To convert by hand, multiply kilometres by 0.62, or multiply by 5 and divide by 8 for a quick estimate (80 km ≈ 50 miles).
Race distances
5K = 3.11 miles, 10K = 6.21 miles, a half marathon (21.0975 km) = 13.1 miles and a marathon (42.195 km) = 26.2 miles. A speed of 100 km/h is about 62 mph.
Frequently asked questions
How many miles is 5 km?
3.107 miles.
How many miles is 10 km?
6.214 miles.
How many km is a mile?
1.609344 km exactly.
How long is a marathon in miles?
26.22 miles (42.195 km).
Is a nautical mile the same?
No. A nautical mile is exactly 1.852 km, used at sea and in aviation.