Unit Converter
Convert between units of length, mass, temperature, area, volume, speed, time, data, energy, power and pressure.
About this calculator
Convert a value from one unit to another across length, mass, temperature, and more. Type a value in any field and the others update instantly.
How linear conversion works
Most units scale by a fixed factor: value × factor = result. For example, meters to feet uses the factor 3.28084.
Temperature is special
Celsius, Fahrenheit, and Kelvin do not share a zero point, so they use offset formulas rather than a simple factor. For example, °F = °C × 9/5 + 32.
Tips
Pick the right category first, then choose the from/to units. Results keep several decimal places so you can round as needed.
How to use Unit Converter
- 1Pick a category: length, weight, temperature, area, volume, speed, time and more.
- 2Enter the value and choose the source and target units. If a unit is missing, switch the category first.
- 3Read the result along with the same value expressed in other common units.
How unit conversion works under the hood
Target = value × (source factor ÷ target factor)Each category has one international base unit: metres for length, kilograms for mass, kelvin for temperature, litres for volume. Every other unit is stored as a single factor saying how many base units it equals. A conversion first turns the input into base units, then divides by the target factor. Adding a unit means registering one factor rather than writing a rule for every pair, and it avoids the rounding drift you get from chaining factors together.
Temperature is the one category that cannot be handled by multiplication alone. Celsius and kelvin differ by an offset (K = °C + 273.15), and Celsius and Fahrenheit use a linear transform with an intercept (°F = °C × 9/5 + 32), so temperature needs its own branch. That is exactly where simple converters go wrong. Watch out too for units that share a name across regions: a US gallon is about 3.785 litres, an imperial gallon about 4.546, a gap of roughly 20%.
| Category | Relationship | Example |
|---|---|---|
| Length | 1 inch = 2.54 cm | 10 in = 25.4 cm |
| Length | 1 foot = 30.48 cm | 6 ft = 182.9 cm |
| Mass | 1 pound = 0.4536 kg | 150 lb = 68.04 kg |
| Volume | 1 US gallon = 3.785 L | 5 gal = 18.93 L |
| Temperature | °F = °C × 9/5 + 32 | 25 °C = 77 °F |
| Speed | 1 mph = 1.609 km/h | 60 mph = 96.6 km/h |
Common conversions at a glance
Frequently asked questions
Why is temperature different from other units?
Because zero is not nothing. Length and mass have absolute zeros, so a single multiplier suffices. Celsius and Fahrenheit define zero differently, with the freezing point of water at 0 and 32, so a conversion needs both a multiplier and an intercept. Multiply 25 by 1.8 without adding 32 and you get 45 instead of the correct 77 °F.
Are US and imperial gallons the same?
No, and the gap is significant. A US gallon is about 3.785 litres while an imperial gallon is about 4.546, roughly 20% more. The same applies to fluid ounces: about 29.57 ml in the US and 28.41 ml in the UK. Always check which system your source uses, because swapping an American recipe into British measures will be visibly off.
How many decimal places should I keep?
This tool keeps enough significant digits for you to round as you like. For everyday use, one decimal is plenty: height to 0.1 cm, weight to 0.1 kg. In engineering or scientific work, match the significant figures of your input data, and do not let an exact defined constant such as 2.54 become the thing that limits your precision.
Is an ounce a weight or a volume?
It can be either, depending on context. The avoirdupois ounce is a mass of about 28.35 grams. The fluid ounce is a volume of about 29.57 ml in the US and 28.41 ml in the UK. Recipes usually mean mass when they write oz, while drink labels mean volume, so read the abbreviation carefully.