How this calculator works
- Step 1To the base× factorTurn the value into metres, kilograms, litres or m/s.
- Step 2To the target÷ factorDivide by the target unit’s size.
- Step 3Exactby definition1 inch is exactly 2.54 cm, 1 pound exactly 0.45359237 kg.
Every unit here is defined exactly in terms of a metric one, so conversions carry no measurement error. Temperatures have an offset as well as a scale, so they use their own formulas.
Worked example: a height of 6 feet
- Length
metres = feet × 0.3048
- 1 foot12 × 2.54 cm0.3048 m
- 6 feet6 × 0.30481.8288 m
In the same way, 150 lb is 68.038856 kg and 60 mph is 96.56064 km/h.
Two gallons
- 10 US gallons37.854118 LUsed in the United States.
- 1 UK gallon1.20095 US galAbout 20% larger than a US gallon.
Body temperature of 98.6 °F is 37 °C: subtract 32, then multiply by 5/9.
Assumptions and limits
- Exact factorsFrom the NIST guide to SI units.
- Six decimalsResults are shown to up to six places.
- Everyday kindsLength, mass, volume, temperature, speed.
- Not land or goldUse the dedicated converters for bigha or tola.
Specialised converters
Some units need their own tool: land, gold, power and data each have local or technical rules.
For Indian land units such as bigha and guntha, use the land area converter. Gold weights are in the gold weight converter, cooling power in the BTU calculator, and data sizes in the bandwidth calculator.
Common mistakes
Mistake: Using a US gallon for a UK recipe.
Instead: Pick UK gallon for imperial measures.
Mistake: Scaling temperature without the offset.
Instead: °F is not twice °C; use the formula.
Mistake: Treating 1 lb as 0.5 kg.
Instead: It is 0.45359237 kg exactly.
Checking the method
A separate script rebuilds every factor from a different chain of exact definitions and checks each golden value.
Read how we test our calculators, or browse more everyday tools.