Measure

A note on accuracy: conversions here use the internationally agreed definitions — an inch is exactly 25.4 millimetres, a pound is exactly 0.45359237 kilograms, and so on — so the arithmetic is exact rather than approximate. Two places to be careful. US and Imperial gallons are different sizes, and both are listed separately because mixing them up is the single most common conversion mistake. And for data, this uses the decimal definitions where a kilobyte is 1,000 bytes, alongside the binary ones where a kibibyte is 1,024 — which is why a drive sold as one terabyte shows up smaller on your computer.