Unit Converter

Exactly 2.54. The inch has been defined as 25.4 millimetres since 1959, so it is an exact figure rather than a measured one — which is why this converter uses it in full instead of rounding. Going the other way, one centimetre is about 0.3937 inches.

Multiply by 2.20462. A pound is defined as exactly 0.45359237 kilograms, so 70 kg is about 154.3 lb and 11 stone is about 69.9 kg. Pick Weight above and the conversion happens as you type.

Because Fahrenheit has both a different scale and a different zero point, and the two scales cross at −40. That crossing is also a good check of any temperature converter: if it does not return −40, it is treating the conversion as a simple ratio and every other answer will be wrong too.

Both conventions exist, which is why both are listed. A kilobyte is 1,000 bytes and a kibibyte is 1,024; storage manufacturers use the first and most operating systems report the second. They differ by 2.4% at kilobytes and about 10% at terabytes, which is why a 1 TB drive shows as roughly 931 GB.

No. Everything is calculated in your browser, so nothing is transmitted and nothing is stored. You can disconnect from the internet after the page loads and it keeps working.

Both. US and UK gallons are listed separately because they are genuinely different — a UK gallon is about 4.55 litres and a US gallon about 3.79, a difference of a fifth. Picking one silently is how a recipe or a fuel figure ends up badly out.