Unit Converter
Convert between metric and imperial units for length, weight, temperature, volume, area and speed, and see the same quantity expressed in every unit of the category at once.
Result
- Kilometers → Miles
- 0.62137119
- 1 km in mi
- 0.62137119
| Unit | Value |
|---|---|
| Millimeters (mm) | 1,000,000 |
| Centimeters (cm) | 100,000 |
| Meters (m) | 1,000 |
| Kilometers (km) | 1 |
| Inches (in) | 39,370.07874 |
| Feet (ft) | 3,280.839895 |
| Yards (yd) | 1,093.613298 |
| Miles (mi) | 0.62137119 |
About this unit converter
Recipes, travel, DIY projects, shipping and school work constantly mix metric and imperial units. This converter covers the six categories people need most often: length, weight, temperature, volume, area and speed. Choose a category, type a number and pick the units; the result and a full table of equivalents update instantly.
How the conversion is done
Each unit has a fixed ratio to a base unit. To convert, the value is multiplied by the source ratio and divided by the target ratio: result = value × factor(from) ÷ factor(to).
Example: 1 kilometer to miles. The base unit for length is the meter: 1 km = 1,000 m and 1 mi = 1,609.344 m, so 1 km = 1,000 ÷ 1,609.344 = 0.621371 mi. Temperature is the exception and uses offset formulas: °F = °C × 9⁄5 + 32, K = °C + 273.15.
Conversion factors used
| Unit | Equals |
|---|---|
| 1 inch | 2.54 cm (exact) |
| 1 mile | 1.609344 km (exact) |
| 1 pound | 0.45359237 kg (exact) |
| 1 stone | 14 lb = 6.35029 kg |
| 1 US gallon | 3.785411784 L (exact); UK gallon 4.54609 L |
| 1 US cup | 8 US fl oz = 236.588 ml |
| 1 acre | 4,046.8564224 m² (exact); 640 acres = 1 mi² |
| 1 knot | 1.852 km/h (exact) |
How to use this converter
- Select the category first; the unit lists change to match it and sensible default units are chosen.
- Use “Swap” to reverse the direction without retyping the value.
- The table under the result lists the value in every unit of the category, useful when you are not sure which unit a document uses.
- For height specifically, the height converter handles feet and inches together; for trip fuel economy in mpg or L/100 km see the fuel cost calculator.
Frequently asked questions
How does unit conversion work?
Every unit in a category is defined as a multiple of one base unit (meters for length, kilograms for mass, liters for volume). A value is multiplied by its unit's factor to reach the base unit and divided by the target unit's factor. For example 1 mile is 1,609.344 m and 1 km is 1,000 m, so 1 mile = 1.609344 km.
Why is temperature different from the other categories?
Celsius, Fahrenheit and Kelvin do not share a zero point, so a simple multiplier is not enough. The converter uses the exact formulas °F = °C × 9/5 + 32 and K = °C + 273.15, which is why 0 °C is 32 °F and −40 °C equals −40 °F.
Are US and UK gallons the same?
No. A US gallon is 3.785 liters while an imperial (UK) gallon is 4.546 liters, about 20% larger. Cups, pints and fluid ounces also differ between the two systems; this converter uses US customary measures for those, and lists the UK gallon separately.
How accurate are the conversions?
The factors are the exact legal definitions where one exists (1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 US gal = 3.785411784 L, 1 acre = 4,046.8564224 m²). Results are shown with up to six significant decimals, which is more than enough for everyday and engineering use.