Weight / Mass Converter
Convert mass between milligrams, grams, kilograms, metric tonnes, ounces, pounds, and stone using exact avoirdupois and metric conversion factors.
How It's Calculated
Formula
\text{result} = \text{value} \times \text{kgPerFromUnit} \div \text{kgPerToUnit}Mass is the amount of matter in an object, measured here in units like kilograms and pounds — distinct from weight, the force gravity exerts on that mass, which this calculator does not compute. Every supported unit converts through one canonical base unit, the kilogram: the input value is first multiplied by its unit's exact kilograms-per-unit factor to get the mass in kilograms, then that kilograms value is divided by the target unit's kilograms-per-unit factor. Metric units (milligram, gram, kilogram, metric tonne) use exact powers of ten. Avoirdupois units are defined from one exact relationship, 1 pound = 0.45359237 kilograms, with ounce (1/16 pound) and stone (14 pounds) derived from it rather than independently approximated.
Worked Examples
Metric to US: 10 kilograms to pounds
- Convert to the base unit: 10 kg (already in kilograms)
- Convert kilograms to pounds: 10 kg / 0.45359237 kg per pound = 22.0462262185... lb
- Result: 10 kg is approximately 22.046226 pounds
US to metric: 1 stone to kilograms
- Convert to kilograms: 1 stone x 14 lb per stone x 0.45359237 kg per lb = 6.35029318 kg
- Result: 1 stone is exactly 6.35029318 kilograms
Frequently Asked Questions
Is this converting weight or mass?
Mass. Kilograms, pounds, ounces, and stone as used here are all units of mass — the amount of matter an object contains. Weight is the force gravity exerts on that mass and varies by location (e.g. on the Moon); this calculator performs a fixed unit conversion, not a gravity-dependent force calculation.
Why convert through kilograms instead of directly between units?
Converting every unit to and from one canonical base unit (the kilogram) means only one conversion factor per unit needs to be defined and verified, instead of a separate factor for every possible pair of units.
Are the pound, ounce, and stone conversion factors exact?
Yes. The international avoirdupois pound is defined as exactly 0.45359237 kilograms. An ounce is exactly 1/16 of a pound, and a stone is exactly 14 pounds, so both are exact derivations of the pound-to-kilogram definition, not independently approximated constants.
Can I convert a negative mass value?
Yes. This calculator treats mass as a generic numeric quantity and converts negative values the same way as positive ones, consistent with how this project's other unit converters (e.g. length) handle negative input.