Free online Unit Converter
Three simple steps
- Choose a measurement category such as length, mass, or temperature.
- Enter the value, then choose the unit you have and the unit you want.
- Read the converted value; use Swap to reverse the unit direction.
Understand your result
Use this converter for length, mass, area, speed, and temperature. Choose a category first so the available units describe the same kind of measurement.
Worked examples
| From | To |
|---|---|
| 1 metre | 3.280839895 feet |
| 1 kilogram | 2.204622622 pounds |
| 1 kilometre per hour | 0.621371192 miles per hour |
| 0°C | 32°F |
| 0 kelvin | −273.15°C |
How a conversion works
For most categories, the calculator converts through a shared base unit: value × source factor ÷ target factor. For example, 1 kilometre is 1,000 metres. Exact definitions are used for common units such as 1 inch = 0.0254 metres and 1 pound = 0.45359237 kilograms.
Temperature uses a different formula
Temperatures require offsets as well as scaling: °F = °C × 9/5 + 32, and K = °C + 273.15. Values below absolute zero (0 K, −273.15°C, or −459.67°F) are rejected.
Precision and limits
Answers are rounded for readability. Very small or very large nonzero values may use scientific notation instead of displaying a misleading zero. Mass uses the avoirdupois ounce and pound; specialist units such as troy ounces and fluid ounces are not included. Currency conversion is not supported.
Measurement reference
NIST: The International System of Units (SI). For regulated, medical, or laboratory work, use the required precision and applicable measurement standard.