How this works
1 mile = 1.609344 km exactly. The factor comes from the international yard-and-pound agreement (1 mile = 5,280 international feet × 0.3048 m). Useful for road-trip planning, marathon distances, and anyone reading US/UK speed limits or odometer readings while in metric countries (or vice versa).
The formula
For mental arithmetic: × 1.6 gives an approximation accurate to ~0.6%. So 100 mph ≈ 160 km/h, 60 mph ≈ 97 km/h, a 26.2-mile marathon ≈ 42.2 km. The "Fibonacci trick" works too — successive Fibonacci numbers approximate the mile-to-km ratio, e.g. 5 mi ≈ 8 km, 8 mi ≈ 13 km, 13 mi ≈ 21 km.
Example calculation
- 1 mi = 1.609 km
- 5 mi = 8.047 km
- 26.2 mi = 42.16 km (marathon)
- 100 mi = 160.9 km
Frequently asked questions
Is "1 mile = 1.6 km" close enough for everyday use?
Yes, for almost any non-precision context. The error is about 0.6% — over a 100 km drive, that's 600 m, less than the length of a typical highway slip-road. For navigation, casual sport, and conversation, 1.6 is fine. Use the exact 1.609344 for engineering, surveying, or anything billed by distance.
How fast is 60 mph in km/h?
60 × 1.609344 = 96.56 km/h. Most US speed limits are quoted as round mph values: 25 mph (residential) ≈ 40 km/h, 45 mph ≈ 72 km/h, 65 mph (highway) ≈ 105 km/h. Speed conversions use the same factor as distance — there's no per-second adjustment because both numerator and denominator scale together.