Km to Miles: The 0.62 Rule and the Fibonacci Trick
A kilometre is 0.621371 miles. But there is a far more elegant way to convert — and it involves the Fibonacci sequence.
2 February 2026 · 4 min read · Distance
One mile is exactly 1.609344 kilometres, which makes one kilometre 0.621371 miles.
The Fibonacci coincidence
The Fibonacci sequence — 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 — has consecutive terms whose ratio approaches the golden ratio, 1.618. The kilometre-to-mile ratio is 1.609. They are within 0.5% of each other.
So any two adjacent Fibonacci numbers convert:
- 5 km ≈ 3 miles (true: 3.11)
- 8 km ≈ 5 miles (true: 4.97)
- 13 km ≈ 8 miles (true: 8.08)
- 21 km ≈ 13 miles (true: 13.05)
- 89 km ≈ 55 miles (true: 55.30)
For numbers in between, decompose: 70 km = 55 + 13 + 2 → 34 + 8 + 1 = 43 miles (true: 43.5).
Race distances
| Race | Kilometres | Miles |
|---|---|---|
| 5K | 5 | 3.107 |
| 10K | 10 | 6.214 |
| Half marathon | 21.0975 | 13.109 |
| Marathon | 42.195 | 26.219 |
| 50K ultra | 50 | 31.069 |
The nautical mile is different
A nautical mile is 1,852 metres exactly — one minute of latitude. It is about 15% longer than a statute mile, which is why a boat doing "20 knots" is moving at 23 mph. See the nautical miles converter.
Speed limits translate too
- 30 mph = 48 km/h
- 50 km/h = 31 mph
- 70 mph = 113 km/h
- 100 km/h = 62 mph
- 130 km/h = 81 mph
Use the km/h to mph converter before you drive abroad.
Related conversions
This article is for general information. Please verify figures against the relevant standard before using them in critical work. About accuracy