The conversions people get wrong
Three pairs cause most of the mistakes. A US gallon is 3.785 litres while an imperial gallon is 4.546 — a 20 % difference that ruins recipes and fuel figures alike. An ounce of weight (28.35 g) is not a fluid ounce of volume. And a ton is 1 000 kg in metric but 907 kg in the US and 1 016 kg in the UK.
Every factor used here is spelled out in the unit names, so you always know which variant you are converting.
Data storage, where the confusion is deliberate
A manufacturer's «1 TB» drive is 1 000 000 000 000 bytes. Your operating system may report it using powers of 1024, which gives 931 «GB» — and people conclude they were short-changed. Neither figure is wrong; they use different definitions of the prefix.
This converter uses decimal prefixes, the ones printed on the box, which is what you want when comparing products.
Frequently asked questions
Which gallon is used?
The US gallon, 3.78541 litres. The imperial gallon of 4.546 litres is a different unit.
Is the conversion exact?
The factors are the internationally defined ones — an inch is exactly 0.0254 m, a mile exactly 1609.344 m. Only the display is rounded.
Does it work without a connection?
Yes, once the page has loaded everything runs on your device.