Unit Converter
Convert between length, weight, temperature, and volume units instantly.
1 m = 3.28084 ft
Convert between units of length, weight, temperature, and volume — metric to imperial and back — covering the everyday conversions people actually look up, from centimetres to inches, kilograms to pounds, or Celsius to Fahrenheit.
Results update as you type, with enough decimal precision to be useful for both quick estimates and more exact measurements.
Conversions worth memorising
| From | To | Multiply by | Quick mental version |
|---|---|---|---|
| Inches | Centimetres | 2.54 (exact) | Double it and add a quarter |
| Miles | Kilometres | 1.609 | Add about 60% |
| Pounds | Kilograms | 0.4536 | Halve it, then add 10% |
| Feet | Metres | 0.3048 | Divide by 3, take off a bit |
| US gallons | Litres | 3.785 | Roughly ×4, minus 5% |
| Ounces | Grams | 28.35 | Roughly ×28 |
Only the inch is defined exactly (2.54 cm by international agreement in 1959); most of the others derive from it.
Why temperature is the odd one out
Length, mass and volume conversions are pure multiplications because all those scales start at a shared zero — zero metres is zero feet. Temperature scales don't share a zero, so converting needs both a multiplication and an offset: °F = °C × 9/5 + 32.
This is why you can say '10 kg is 22 lb' but you cannot say '10 °C is 50 °F' in the sense of a ratio — a 10-degree Celsius rise is an 18-degree Fahrenheit rise, but 10 °C itself is 50 °F. The two facts use different arithmetic, and conflating them is the classic error. The scales cross at −40, which is the same temperature in both.
Units that share a name but not a size
- Gallons: a US gallon is 3.785 L, an imperial gallon 4.546 L — a 20% difference that ruins recipes and fuel calculations alike.
- Fluid ounces: the US fluid ounce is 29.57 ml, the imperial 28.41 ml. Confusingly, the imperial pint holds 20 fl oz and the US pint 16.
- Tons: a US short ton is 2,000 lb, a UK long ton 2,240 lb, and a metric tonne 1,000 kg (about 2,205 lb).
- Miles: the nautical mile (1,852 m) is longer than the statute mile (1,609 m), and is what aviation and shipping use.
- Cups: a US cup is 240 ml, a metric cup 250 ml, a Japanese cup 200 ml. For baking, weigh ingredients instead.
Frequently asked questions
- Why is temperature conversion different from the others?
- Length, weight, and volume conversions are simple multiplications, but temperature scales have different zero points, so converting Celsius to Fahrenheit requires both multiplying and adding an offset (°F = °C × 9/5 + 32).
- How precise are the conversions?
- Conversions use standard, internationally defined conversion factors (e.g. 1 inch = 2.54 cm exactly) and display several decimal places for accuracy.
- Can I convert between two imperial units, like feet to inches?
- Yes — the converter isn't limited to metric-to-imperial; it handles conversions between any two units within the same category.
- Is a US gallon the same as a UK gallon?
- No. An imperial (UK) gallon is 4.546 litres and a US gallon is 3.785 — about 20% smaller. Check which one a recipe or fuel figure means before converting.
- At what temperature are Celsius and Fahrenheit the same?
- −40. It's the one point where the two scales cross, which makes it a useful sanity check on any conversion formula.