Weight & Mass Converter
Convert between every common weight unit — metric (mg, g, kg, tonne), imperial (oz, lb, stone, ton), plus carats and grains used in jewelry and ammunition.
Enter a weight
How to use this calculator
1. Enter the value
Type the number you want to convert. Decimals are fine.
2. Pick the source unit
The dropdown is grouped by family: metric (mg → tonne), imperial (oz → long ton), and specialty (carat for gems, grain for bullets).
3. Use presets for common cases
Quick chips fill values like body weight in pounds or stones, or a one-kilogram reference.
4. Read across the grid
Eight common equivalents show simultaneously. Carat and grain are calculated too — they're encoded in the share URL even though they aren't displayed in the grid.
About weight units
Mass vs. weight
Technically, "mass" is what you measure on a balance (a property of the object). "Weight" is mass × gravity. In everyday usage on Earth the two terms are interchangeable — this tool follows that convention.
Key exact conversions
1 lb = 453.59237 g (exact by definition since the 1959 international agreement). 1 oz = 1/16 lb. 1 stone = 14 lb. 1 carat = 200 mg exactly. 1 short ton = 2,000 lb; 1 long ton = 2,240 lb.
Avoirdupois vs. troy
This calculator uses the avoirdupois system (everyday weights). For precious metals, the troy ounce (≈ 31.10 g, heavier than the standard oz) is the convention — convert with care when buying gold or silver.