All-in-One Unit Converter

Convert the quantity, keep the meaning

Start with a measurement type, enter a value, then choose its original and destination units. Swap units reverses the selected pair while leaving your input unchanged, so you can compare the factors in both directions. Results show up to 12 significant digits; this display precision does not make a rough measurement more accurate.

Three easy mistakes to avoid

• US versus imperial volume: one US gallon is 3.785411784 litres; one imperial gallon is 4.54609 litres. Pick the country’s unit rather than assuming “gallon” has one meaning. The cup here is a US customary cup, not a 250 ml metric cup.
• Decimal versus binary storage: 1 GB = 1,000,000,000 bytes, while 1 GiB = 1,073,741,824 bytes. A 1 GB quantity is about 0.931323 GiB. Neither conversion adds or removes data.
• Area versus length: 1 foot = 0.3048 metres, but 1 square foot = 0.09290304 square metres. Area needs the squared factor.

How the calculation works

For most categories, value × source factor ÷ destination factor gives the converted value. The factors are relative to metres, kilograms, litres, square metres, seconds, or bytes. Temperature needs an offset: °C = (°F − 32) × 5 ÷ 9, and K = °C + 273.15. Negative temperatures are allowed down to absolute zero; other quantities use non-negative inputs.

References: NIST conversion factors and NIST binary prefixes. Liquid volume definitions are also tabulated in NIST Handbook 44, Appendix C.

What this tool cannot convert

Mass and volume cannot be exchanged without density: 100 ml of oil need not weigh 100 g. Days here are fixed 24-hour durations, not calendar dates or daylight-saving transitions. Months and years are intentionally omitted because their duration depends on context. Currency conversion needs a dated exchange-rate source and is not part of this tool.

For more focused examples, try inches and centimetres or read metric and imperial conversions.