Convert kilometers to miles

The formula

miles = kilometers × 0.62137119

kilometers to miles — quick reference

Consecutive Fibonacci numbers convert kilometres to miles almost exactly

5 km is about 3 miles, 8 km about 5, 13 about 8, 21 about 13 - every adjacent pair in the Fibonacci sequence is a working conversion. The reason is that the ratio between consecutive Fibonacci numbers settles on 1.618, and a mile is 1.609 kilometres, so the trick holds to within roughly half a per cent.

Numbers outside the sequence can be broken into pieces: 70 km is 55 plus 13 plus 2, which maps to 34 plus 8 plus 1.2, giving 43.2 miles against a true 43.5. If that is more arithmetic than the moment allows, multiplying by 0.6 gets within three per cent, always slightly short.

Race distances are defined in metric, so the mile figures are the rounded ones

A 5K is 3.107 miles and a 10K is 6.214. The half marathon is 21.0975 km, or 13.109 miles, and the marathon is 42.195 km - 26.219 miles. Those distances are fixed by World Athletics in metres, which is why the imperial equivalents are so awkward: 26.2 is a rounding of the real number, not a definition of it.

Speeds behave the same way. A 100 km/h limit is 62 mph, the common European motorway 130 km/h is 81 mph, and an urban 50 km/h is 31 mph. Worth knowing before trusting a hire car’s dial: type-approval rules require a speedometer never to read below true speed, so it will usually flatter you by a few per cent.

Questions