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Convert length, mass, temperature, area, volume, and speed as you type — with the conversion factor shown.
Metric and US customary length units. 1 in = 2.54 cm and 1 mi = 1.609344 km exactly.
1 km = 0.6213711922 mi
Choose length, mass, temperature, area, volume, or speed, then enter an amount and select the starting and target units. The result updates immediately; use Swap units to reverse the conversion and carry the result into the new input.
Most conversions multiply by the size of the starting unit and divide by the size of the target unit in the same measurement category. Temperature needs an offset as well as a scale: °F = °C × 9/5 + 32, °C = (°F − 32) × 5/9, and K = °C + 273.15. Area conversion factors are squared length factors, while volume factors are cubed.
Choose Length, enter 2.5, and select km to m. Since 1 km = 1000 m, 2.5 × 1000 = 2500 m.
Choose Temperature, enter 100, and select °C to °F. Calculate 100 × 9/5 + 32 = 212 °F.
Choose Volume, enter 1, and select US gallon to litre. One US liquid gallon is 3.785411784 L; this is not an Imperial gallon.
The liquid gallon, cup, and fluid ounce are US customary measures. A ton means a US short ton of 2000 lb, not a metric tonne or British long ton.
Not directly. Mass and volume are different categories; you need the material’s density to connect them. Choose units within the same category in this converter.
The supported temperature scales represent physical temperatures. Absolute zero is 0 K, −273.15 °C, or −459.67 °F; those boundaries are accepted, but lower values are not.
Conversions use floating-point numbers. Most results display up to 10 significant digits, while temperature keeps up to 15. Display rounding is not a statement about the precision of your original measurement.
Use the ratios lesson to understand conversion factors. For measurements that feed into shape calculations, convert all lengths to the same unit before using the area or volume tools below. Related tools: Ratio Calculator, Area and Perimeter Calculator. Read the ratios lesson on conversion factors or practice ratios & proportions to build confidence without relying on a calculator. For measurement formulas, also read the Surface Area & Volume lesson.