🛣️ Distance Converter
Convert between kilometers (km) and miles
Written by Albert Mateos · Founder & Editor
Last reviewed: May 2, 2026
Formula: 1 km = 0.621371 miles | 1 mile = 1.60934 km
Origin of the units
The mile descends from the Roman mille passus — "a thousand paces," where a pace was a double step of about 5 Roman feet. Roman miles measured roughly 1,479 m. The English statute mile was fixed by an Act of Parliament in 1593 at 5,280 feet, and the modern international mile was formalized under the 1959 International Yard and Pound Agreement as exactly 1,609.344 m. The kilometre is a metric-system unit: 1 km = 1,000 m, with the metre defined since 1983 by the speed of light in vacuum. Every km ↔ mile conversion is therefore mathematically exact: 1 mile = 1.609344 km and 1 km = 0.621371 miles.
Why these conversions matter in fitness
Running, cycling, and rucking all live across the unit divide. American road races traditionally use miles (the marathon's 26.2 miles, the 5-mile and 10-mile classics), while almost every other country reports the same distances metrically (the 5K, 10K, 21.0975 km half-marathon, 42.195 km marathon). Treadmills sold in the US default to mph and miles; treadmills sold in Europe default to km/h and km. Pace conversions are where runners stumble most: a 6:00 min/km pace is not the same as a 6:00 min/mile pace — the first is a moderate jog (about 9:39 min/mile), the second is a serious sub-2:40 marathon pace. GPS watches let you switch displays, but workout descriptions, race recaps, and training plans freely mix the two.
Common rounding & accuracy notes
For training, rounding to 0.1 km or 0.1 mile is appropriate — GPS error alone is typically 1–3% of distance under tree cover or in urban canyons. The handy approximation "5 km ≈ 3.1 miles" is correct to four significant figures. For race distances, the official numbers are exact and certified by World Athletics: a marathon is exactly 42.195 km, a half-marathon exactly 21.0975 km. Pace conversion runs in the inverse direction of distance: if you slow your km pace by 30 seconds, your mile pace slows by about 48 seconds (the ratio is 1.609344). When converting splits, do the time-per-distance math in seconds, not in clock notation, to avoid base-60 mistakes.
Quick reference table
| Distance | Kilometres | Miles |
|---|---|---|
| Track lap (outdoor) | 0.400 km | 0.249 mi |
| 1 mile | 1.609 km | 1.000 mi |
| 5K | 5.000 km | 3.107 mi |
| 10K | 10.000 km | 6.214 mi |
| 10 miles | 16.093 km | 10.000 mi |
| Half-marathon | 21.098 km | 13.109 mi |
| Marathon | 42.195 km | 26.219 mi |
| 50K ultra | 50.000 km | 31.069 mi |
| 50 mile ultra | 80.467 km | 50.000 mi |
| 100K ultra | 100.000 km | 62.137 mi |
| 100 mile ultra | 160.934 km | 100.000 mi |
How it works
Convert between kilometers (km) and miles instantly with this free bidirectional distance converter. The formula: multiply km by 0.621371 to get miles, or multiply miles by 1.60934 to get km. Great for runners tracking race distances, cyclists, road trips, or anyone converting between metric and imperial units. Fast, free, no sign-up required.
Frequently Asked Questions
- How do I convert kilometers to miles?
- Multiply kilometers by 0.621371 to get miles. A handy approximation is to multiply by 0.6 or remember that 5 km is roughly 3.1 miles and 10 km is about 6.2 miles. This is especially useful for converting race distances and running routes.
- Why are race distances in kilometers?
- Most international races use metric distances (5K, 10K, half marathon at 21.1 km). The marathon distance of 26.2 miles (42.195 km) is one of the few races commonly referenced in miles, particularly in the US. Track events at the Olympic level use meters exclusively.
- What is the difference between a nautical mile and a regular mile?
- A nautical mile equals 1.852 km or about 1.151 regular (statute) miles. Nautical miles are used in aviation and maritime navigation because they correspond to one minute of latitude. This converter handles standard kilometers-to-miles conversions for land-based distances.