Unit converter
Length, weight, temperature, volume, area and speed, converted instantly in both directions with the exact factor shown under every answer.
Guide
How to use it
- Pick the measurement type: length, weight, temperature, volume, area or speed.
- Choose the from and to units, or hit the swap button to flip them.
- Type in either box; the other side updates as you type.
- Read the grey factor line to repeat the maths anywhere, and watch for the blue extras: stones get a stones-and-pounds readout, inches get feet-and-inches.
Examples
Worked examples
5 km ÷ 1.609344 = 3.10686 miles. Parkrun distance, for anyone raised on miles.
2 US pints = 0.946 litres, noticeably less than 2 UK pints (1.137 litres). Volume has two English-speaking systems; the converter lists both.
A quarter-acre plot is 4046.86 ÷ 4 = 1,011.7 m². Area factors are squares of length factors, which is why they look unwieldy.
Method
How it works
Every unit is stored as its exact ratio to a base unit (metres, kilograms, litres, square metres, metres per second), so any conversion is one multiply and one divide with no chained rounding. Temperature is the exception, converted through Celsius with the standard offset formulas. Results show up to six significant figures.
The definitions are the international standards: an inch is exactly 25.4 mm, a pound exactly 0.45359237 kg, a UK gallon exactly 4.54609 litres. Everything runs on your device.
FAQ
Frequently asked questions
How accurate are the conversions?
Exact. Factors use the international definitions (an inch is exactly 25.4 mm, a pound exactly 0.45359237 kg) and results show up to six significant figures.
Why are UK and US pints different?
The countries standardised different gallons in the 1800s. A UK pint is 568 ml, a US pint 473 ml, so recipe conversions need the right one, both are listed separately.
Which conversions do people use most?
Height and body weight (cm to inches, kg to stone), driving distances (miles to km) and temperatures (Celsius to Fahrenheit). Each has its own page with worked examples.
Why does temperature not use a simple factor?
Because the scales start at different zeros. Fahrenheit needs a multiply and a shift (9/5 then +32), which is why 0 °C is 32 °F, not 0.
Can I convert both directions?
Yes, type in either box. The other side updates instantly, and the swap button flips the units.
Does it work offline?
Yes. The factors are built into the page, so once loaded it needs no connection and nothing you type is transmitted.
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