OnlineFreeToolBoxHow-to guide
How to Convert Units Online Free
Millimetres or inches? Kilograms or pounds? Celsius or Fahrenheit? This guide shows how to convert units — length, weight and temperature — for free, in your browser, with the exact definitions the converter uses. Use the free unit converter below to convert any unit in seconds.
How to Convert Units — step by step
- Pick a category: Length, Weight or Temperature.
- Enter the value in the “Value” field.
- Choose the starting unit in the “From” list.
- Choose the target unit in the “To” list (or press the swap button to reverse them).
- Press “Convert” and read the result — it also updates live as you type.
Tips
- Length covers millimetres to miles, weight covers milligrams to stones, and temperature covers Celsius, Fahrenheit and Kelvin.
- 1 inch is exactly 2.54 centimetres, and 1 mile is about 1.609 kilometres.
- Press the swap button to reverse the conversion without retyping the value.
Frequently asked questions
Which units are supported?
Length units: millimetres, centimetres, metres, kilometres, inches, feet and miles.
How many centimetres are in an inch?
Exactly 2.54 centimetres. That exact definition is what the converter uses.
Can I convert miles to kilometres?
Yes. Choose miles as the “From” unit and kilometres as the “To” unit — 1 mile is about 1.609 kilometres.