Miles to Kilometers
Convert miles (mi) to kilometers (km). Both measure distance and dimension, and the conversion comes up in construction, navigation, sports work.
The Formula
``
kilometers = miles × 1.609344
miles = kilometers × 0.621371192237
`
One mile is 1.6093 kilometers, and one kilometer is 0.621371 miles.
Conversion Table
| Miles | Kilometers |
|---|---|
| 1 mi | 1.6093 km |
| 2 mi | 3.2187 km |
| 5 mi | 8.0467 km |
| 10 mi | 16.0934 km |
| 25 mi | 40.2336 km |
| 50 mi | 80.4672 km |
| 100 mi | 160.9344 km |
| 500 mi | 804.672 km |
| 1,000 mi | 1,609.34 km |
The Other Direction
| Kilometers | Miles |
|---|---|
| 1 km | 0.621371 mi |
| 2 km | 1.2427 mi |
| 5 km | 3.1069 mi |
| 10 km | 6.2137 mi |
| 25 km | 15.5343 mi |
| 50 km | 31.0686 mi |
| 100 km | 62.1371 mi |
| 500 km | 310.6856 mi |
| 1,000 km | 621.3712 mi |
What Each Unit Is
Miles (mi) — exactly 1,609.344 metres, by the 1959 international yard and pound agreement. The Roman mille passus — a thousand paces — later fixed by English statute at 5,280 feet.
Kilometers (km) — 1,000 metres. The metric system’s road-scale unit, adopted across most of the world in the 19th century.
A Sense of Scale
A brisk walk covers a mile in 15 minutes- A marathon is 26.2 miles
- US speed limits are in mph
- A 20-minute walk covers about 1.5 km
- A marathon is 42.195 km
- A cruising airliner flies at 11 km
Doing It in Your Head
Multiply by 8, then divide by 5. That is off by 0.58% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 16.0934 km 16 km 160.9344 km 160 km
Precision
The factor 1.609344 is exact by international agreement, not a rounded approximation. Any imprecision in a result comes from your input, not the conversion.
In Code
`javascript
const mileToKilometer = (value) => value * 1.609344;
``
Where This Conversion Comes Up
- Construction
- Navigation
- Sports
- Sewing
- Mapping
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 mi with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 mi becomes | Error |
|---|---|---|---|
| 0 | 2 | 274 | 24.2742% |
| 1 | 1.6 | 219.2 | 0.5806% |
| 2 | 1.61 | 220.57 | 0.0408% |
| 3 | 1.609 | 220.433 | 0.0214% |
| 4 | 1.6093 | 220.474 | 0.0027% |
The right number of significant figures is set by your input, not by the converter. If you measured miles to three significant figures, the answer in kilometers is only good to three — writing more digits claims precision the measurement never had.