How many kilometers is a marathon?

A marathon is 26.2 miles in round numbers, which is 42.164688 kilometers. The official distance is defined in metric as 42.195 kilometers, so the mile figure is the approximation, not the other way round.

Is 60 mph the same as 100 km/h?

Almost. 60 miles per hour is 96.56064 km/h, so a 100 km/h limit is slightly faster than 60 mph. The two are close enough that speedometers show both, but they are not equal.

Why 1.609344 and not 1.6?

Because the international yard was fixed at exactly 0.9144 meters in 1959, and a mile is 1760 yards. That makes 1609.344 meters an exact definition. Using 1.6 introduces an error of about nine meters over ten miles.

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Miles to Kilometers

Convert miles to kilometers in your browser. One mile is exactly 1.609344 kilometers, so the answer is a fixed ratio rather than an approximation.

km = mi × 1.609344

NIST SP 811 (2008), Appendix B.8 — mile (mi) to kilometer (km) = 1.609 344 E+00

Going the other way from kilometers is the conversion most travellers need: road signs across Europe, Asia and most of Africa are in kilometers, while distances quoted in the United States and the United Kingdom are in miles. Multiplying by 1.609344 is exact, which is why "add about 60 percent" is a decent mental shortcut and why it drifts once the numbers get large.

How it is calculated

km = mi × 1.609344

This is the factor exactly as the standard states it, so no division and no rounding are involved. The rough version people use in their head, multiply by 1.6, is short by roughly six meters per mile.

Source: NIST SP 811 (2008), Appendix B.8 — mile (mi) to kilometer (km) = 1.609 344 E+00

Common values

miles	kilometers
1	1.609344
2	3.218688
3	4.828032
5	8.04672
10	16.09344
13.1	21.082406
20	32.18688
26.2	42.164813
50	80.4672
60	96.56064
100	160.9344

Questions people ask

How many kilometers is a marathon?: A marathon is 26.2 miles in round numbers, which is 42.164688 kilometers. The official distance is defined in metric as 42.195 kilometers, so the mile figure is the approximation, not the other way round.
Is 60 mph the same as 100 km/h?: Almost. 60 miles per hour is 96.56064 km/h, so a 100 km/h limit is slightly faster than 60 mph. The two are close enough that speedometers show both, but they are not equal.
Why 1.609344 and not 1.6?: Because the international yard was fixed at exactly 0.9144 meters in 1959, and a mile is 1760 yards. That makes 1609.344 meters an exact definition. Using 1.6 introduces an error of about nine meters over ten miles.

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