Unit Converter

Convert between units in the same category

Choose a category, select source and destination units, and enter a numeric value. The result updates as you edit. Categories cover length, mass, volume, temperature, area, speed, pressure, and energy. The tool does not convert between different physical quantities, such as volume and mass, without additional information.

Steps

1. Select the required category. On a phone, scroll the category buttons horizontally to see more choices.
2. Select a source unit and a destination unit; both are required.
3. Enter the value and inspect the result.
4. Use the swap button to reverse the units. Copy the output when you need it elsewhere.

Changing a category clears the selected units and result, so choose both units again. Enter digits rather than unit text in the value field.

Representative examples

The output removes unnecessary decimal zeros. Six displayed decimal places are a presentation choice, not proof that every stored conversion factor has six-place measurement accuracy.

Multiplicative factors and temperature offsets

Most conversions use a base-unit factor: result = value × source factor / destination factor. Area and volume require their own factors; a length conversion must not be applied directly to squared or cubed units.

Temperature uses offsets as well as scale: °F = °C × 9/5 + 32 and K = °C + 273.15. That is why doubling a Celsius number is not equivalent to doubling an absolute temperature.

Which gallon, cup, ton, and Mach?

This implementation uses US liquid volume factors: approximately 3.78541 L per gallon and 236.588 mL per cup. These are not Imperial gallons or every regional cup definition. The mass unit labeled ton is the metric tonne, equal to 1000 kg.

Mach is represented by a fixed factor of 343 m/s in this general converter. The physical speed of sound varies with conditions, so this fixed assumption is unsuitable for determining an aircraft's actual Mach from changing atmospheric conditions.

Some factors are stored as rounded constants. For regulated measurements, calibration work, or calculations sensitive to factor precision, use the definition and precision required by that context. NIST Handbook 44, Appendix C provides reference tables and distinguishes US and British units.

Troubleshooting and next steps

If the result is empty, check that both units are selected and the input is numeric. Unexpected volume results often come from mixing unit definitions. A temperature outside a physical range is not automatically a validated measurement; check the meaning of your source input.

For adjustable kilogram/pound precision, use the dedicated kg to lb converter. Use the scientific calculator for additional calculations after converting.