Calculator
Weight Converter
Convert between metric and imperial weight units.
How do metric and imperial weight units relate?
Metric weight units scale by powers of 10 (1,000mg = 1g, 1,000g = 1kg), the same clean structure as metric length. Imperial weight uses 16 ounces to a pound, and there are even two different definitions of "ton" depending on which system you’re in — a common source of confusion this calculator avoids by treating each unit explicitly.
Frequently asked questions
What is the exact pound-to-kilogram conversion?
1 pound = 0.45359237 kilograms exactly, by international agreement since 1959 — the same standardization year as the inch-to-centimeter definition. Every other pound/ounce conversion to metric derives from this exact value.
Is a "ton" the same everywhere?
No, and this is a common source of error. A metric ton (tonne) is 1,000 kg. A US short ton is 2,000 lb (about 907 kg). A UK long ton is 2,240 lb (about 1,016 kg). All three are meaningfully different, so it matters which one a source is referring to.
Is weight the same as mass?
Technically no — mass is the amount of matter in an object and stays constant everywhere, while weight is the force of gravity on that mass and changes with gravity (an object weighs less on the Moon but has the same mass). In everyday use, including this calculator, "weight" units like kg and lb are used interchangeably with mass, which is standard practice on Earth.
Why do grams and ounces conversions look uneven?
1 ounce = 28.3495 grams, a conversion that doesn't round to anything clean because the two systems weren't designed to align. This is the same underlying reason length conversions like miles-to-km produce long decimals — metric and imperial units have independent historical origins.