Weight & Mass Converter
Convert kilograms, pounds, grams, ounces, stone and tonnes.
About weight units
Everyday language says weight where physics says mass, and this category covers units of mass: kilograms, grams, pounds, ounces, stone and tonnes. The link between metric and imperial is exact — one pound is defined as exactly 0.45359237 kilograms. Units of force such as the newton and pound-force are in the Force category.
These units measure mass. Pounds and ounces mean avoirdupois unless the unit explicitly says troy; a fluid ounce measures volume and requires a density to relate it to mass.
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Compare unit values in the base unit. Numbers are rounded to 8 significant digits; conventions and assumptions appear beside the units.
| Unit | Symbol | 1 unit in kg |
|---|---|---|
| kilogram | kg | 1 |
| gram | g | 0.001 |
| milligram | mg | 0.000001 |
| microgram | µg | 1e-9 |
| tonneDistinct from the US short ton (2,000 lb) and the imperial long ton (2,240 lb). | t | 1,000 |
| pound | lb | 0.45359237 |
| ounceA unit of mass. The fluid ounce is a unit of volume and lives in the Volume category. | oz | 0.028349523 |
| stone | st | 6.3502932 |
| US ton | ton | 907.18474 |
| imperial ton | long tn | 1,016.0469 |
| caratNot the same as karat, which measures gold purity rather than mass. | ct | 0.0002 |
| grain | gr | 0.00006479891 |
| troy ounceAbout 10% heavier than the avoirdupois ounce used for everyday goods. | ozt | 0.031103477 |
| troy pound | lbt | 0.37324172 |
| atomic mass unitUses the CODATA 2022 atomic mass constant, 1.66053906892 × 10⁻²⁷ kg, with standard uncertainty 0.00000000052 × 10⁻²⁷ kg. This kilogram value is measured, not exact. | u | 1.6605391e-27 |
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Each page has the formula, worked examples and a reference table.