Kilometre to Mile Converter
Convert km to miles instantly. Free km to miles calculator with formula, examples and FAQs.
Quick answer
1 km equals 0.621371 miles. To convert km to miles, multiply the km value by 0.621371 — so 10 km = 6.21371 miles. This factor is exact, and the reverse conversion (miles to km) simply divides by 0.621371 instead of multiplying.
Converted value
0.62
1.00 km = 0.62 miles
What is km to miles?
km to miles is a length conversion: the measured amount does not change, just the way it is expressed. It matters most to travellers, runners and anyone using metric maps. A single conversion factor (miles = km × 0.621371) handles any value, large or small.
Real-world uses: why convert km to miles?
Converting km to miles bridges two ways of measuring the same thing. People do it most often when converting marathon and race distances for training, and on the receiving side when comparing international travel distances. Having the exact value — not a rough estimate — prevents costly mistakes in paperwork, purchases and planning.
- •Planning road trips and reading distance on highway signs.
- •Logging running and cycling distances from a GPS watch.
- •Checking map and navigation distances abroad.
- •Converting marathon and race distances for training.
- •Comparing international travel distances.
Who uses this conversion?
How the km to miles conversion is calculated
This is the same arithmetic that calculators and search engines use — no rounded shortcuts.
miles = km × 0.621371
- Both km and miles are defined in terms of the same base unit, the metre.
- 1 km = 1000 metre, and 1 miles = 1609.344 metre.
- Divide one definition by the other to get the conversion factor: 1000 ÷ 1609.344 = 0.6213712.
- So miles = km × 0.621371. Multiply any km value by 0.6213712 to get the result in miles.
Precision: The conversion factor is exact by international definition, so the result is an exact rational number. We display it rounded to four decimal places (or four significant figures for very small values).
Example calculations
- •5 km = 3.1069 miles
- •10 km = 6.2137 miles
- •42 km = 26.0976 miles
km to miles quick reference table
Common km values converted to miles, each calculated with the exact factor.
| km | miles |
|---|---|
| 10 | 6.2137 |
| 25 | 15.5343 |
| 50 | 31.0686 |
| 100 | 62.1371 |
| 250 | 155.3428 |
| 500 | 310.6856 |
| 1000 | 621.3712 |
| 2500 | 1553.428 |
| 5000 | 3106.856 |
| 10000 | 6213.7119 |
Common mistakes to avoid
- •Reading the result the wrong way round. Confirm the answer is in miles, not km, before you rely on it.
- •Truncating instead of rounding, which compounds error across larger km values.
- •Mixing metric and imperial units midway through a multi-step conversion instead of converting to a single base unit first.
Common questions about length conversions
Is this length conversion exact?
Yes. Factors such as 1 inch = 25.4 mm and 1 mile = 1,609.344 m are exact by international agreement, so the only rounding is in how many decimals we display.
Why do my results differ slightly from another tool?
Almost always because the other tool rounds the factor (e.g. 0.62 instead of 0.621371) or rounds partway through. We keep full precision and round only the final value.
Metric or imperial — which should I use?
Use metric (m, cm, km) for science and most countries, and imperial (ft, in, miles) for US and UK everyday distances. This page bridges the two exactly.
Can I round the answer?
Yes. For everyday use one or two decimals is plenty; engineering and science may need more. Round only at the end to avoid cumulative error.
History of these units
History of the kilometre
metric
The kilometre arrived with the metric system in 1790s France as 1,000 metres, the metre itself first defined as one ten-millionth of the distance from the equator to the North Pole. It is now the standard unit for road distance across most of the world.
History of the mile
imperial / US customary
The mile descends from the Roman mille passus — 'a thousand paces', roughly 1,480 metres. The modern international mile was fixed at exactly 1,609.344 metres in 1959 and remains standard for road distance in the US and UK.
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Frequently asked questions
How do I convert km to miles?
What is 1 km in miles?
How many miles is a 5K or 10K run?
How do I convert miles back to km?
When would I need to convert km to miles?
Is the km to miles factor exact?
Is my data private when I use this km to miles converter?
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