About this unit converter
This converter handles the three conversions people need most: length (metric and imperial), weight, and temperature. All factors are the exact international definitions — an inch is exactly 25.4 mm, a pound is exactly 0.45359237 kg — so results are safe to use for work, study, cooking, travel and online shopping size charts.
How to use it
- Choose a category: Length, Weight or Temperature.
- Type the value you have.
- Pick the 'From' and 'To' units — the result appears instantly. Use Swap to reverse the conversion.
The formula
Temperature: F = C x 9/5 + 32 · C = (F - 32) x 5/9 · K = C + 273.15
Worked example
Frequently asked questions
How many millimetres are in an inch?
Exactly 25.4 mm. The inch has been defined as exactly 25.4 millimetres since 1959, so conversions between inches and metric units are exact, not approximations.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. For example, 100°F is (100 - 32) x 5/9 = 37.78°C. Or just enter it above.
Is a US ton the same as a metric tonne?
No. This converter uses the metric tonne (1,000 kg). A US (short) ton is 2,000 lb = 907.18 kg, and a UK (long) ton is 2,240 lb = 1,016.05 kg.
Why does the result show many decimal places?
Some conversions produce repeating decimals. Results are rounded to at most 6 decimal places, which is more precision than everyday measurements need.