Free Unit Converter
A unit converter changes a measurement from one unit to another, such as kilometres to miles or kilograms to pounds. This free converter covers ten categories: length, weight, area, volume, speed, temperature, pressure, power, torque and digital storage. It uses exact conversion factors and can show your value in every unit of the category at once.
Unit Converter
Calculators and Converters
About this tool
Pick the value, the unit you have and the unit you want. If you choose "All units in the category" as the target, the tool lists your value in every unit of that category, which is useful when you are not sure which unit a spec sheet or recipe uses. Each unit is defined by its exact factor to the SI base unit, for example one inch is exactly 0.0254 metres and one pound is exactly 0.45359237 kilograms, so results stay consistent when you convert back and forth.
A few units are easy to mix up. A US gallon (3.785 litres) is smaller than an imperial gallon (4.546 litres). A kilobyte is 1,000 bytes in storage marketing but a kibibyte is 1,024 bytes, which is why a "500 GB" drive shows less in an operating system that counts in powers of 1,024. Temperature is converted with formulas, not a single factor, because Celsius, Fahrenheit and Kelvin start from different zero points.
If a conversion is part of a bigger job, such as sizing a print banner, comparing hosting storage plans or checking a product spec for a store, round the result only at the end. Rounding at each step builds up small errors. For anything where safety or billing depends on the number, such as pressure ratings or engine power, confirm the figure against the manufacturer's own documentation.
Frequently asked questions
How do I convert kilometres to miles?
Choose Length, enter the distance, pick Kilometre as the unit you have and Mile as the target, then convert. One kilometre is 0.621371 miles, because one mile is exactly 1,609.344 metres. The tool does the arithmetic with the exact factor, so you can also read the same value in feet, yards and other length units.
What is the difference between MB and MiB?
A megabyte (MB) is 1,000,000 bytes and a mebibyte (MiB) is 1,048,576 bytes. Storage makers use the decimal units, while many operating systems report in powers of 1,024, which is why a drive seems to hold less than advertised. Both are available here so you can see the exact gap.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9, divide by 5 and add 32. For example, 100 degrees Celsius is 212 degrees Fahrenheit and 0 degrees Celsius is 32. The converter applies this formula for you, and handles Kelvin and Rankine in the same way, so the result is right for negative temperatures too.
Is a US gallon the same as an imperial gallon?
No. A US gallon is 3.785411784 litres, while an imperial (UK) gallon is 4.54609 litres, about 20 percent larger. Fuel economy figures, paint tins and recipes can use either, so check which one a source means before you convert. Both gallons, quarts and pints are included here.
Why do some results show many decimals?
The tool keeps up to ten significant digits so that small units, such as millimetres in a kilometre, are not rounded to zero. Very large or very small answers switch to scientific notation, written like 1.5e-7. Round the figure to the precision you need after you copy it.