Running and cycling distances, US and UK road signs and speed limits, and the unit settings on running apps and smartwatches may all use miles. Race distances in particular are often quoted both ways: 5K, 10K, the half marathon (21.0975 km) and the marathon (42.195 km) are about 3.1, 6.2, 13.1 and 26.2 miles.
Formula: mi = km ÷ 1.609344 ≈ km × 0.621371. Example: 10 km = 6.21 mi. Table values are rounded to two decimal places (one for temperatures); use the converter above for more precision.
Multiply kilometers by 0.6 for a rough answer: 100 km is about 60 miles (exactly 62.14). Fibonacci numbers make a handy approximation too: 5 km ≈ 3 mi, 8 km ≈ 5 mi, 13 km ≈ 8 mi. Speeds work the same way: 100 km/h is about 62 mph.
