Mass calculator
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Mass measures the amount of matter in an object. The SI base unit is the kilogram (kg), redefined in 2019 in terms of the Planck constant. Common mass units include grams, kilograms, tonnes (metric), and ounces, pounds, stones, US/UK tons (imperial). 1 kg equals 2.20462 pounds.
Open the live mass converter for any input value.
In everyday speech, 'weight' and 'mass' are used interchangeably, and for unit-conversion purposes that's fine. In strict physics, mass measures the amount of matter (kilograms, pounds-mass), and weight is the gravitational force acting on that mass (newtons, pounds-force). On Earth at sea level, a 1 kg object weighs about 9.81 newtons.
For body weight, food, shipping, and almost every commercial context, treat pounds and kilograms as mass units. The pound is defined as exactly 0.45359237 kg, fixed by the 1959 international yard and pound agreement.
The metric system uses the gram as the conceptual base unit and the kilogram as the SI base. Decimal prefixes apply consistently: milligram (10^-3 g), gram (10^0 g), kilogram (10^3 g), megagram or 'tonne' (10^6 g, also called the 'metric ton'). The tonne is 1,000 kg or about 2,204.62 lbs.
Pharmaceuticals, jewelry, and scientific work use smaller subdivisions: milligram (mg), microgram (μg or mcg), nanogram (ng). Drug dosing in milligrams per kilogram of body weight is common, which is why precise body-weight conversion matters in medicine.
The avoirdupois pound (453.59237 g) is the everyday unit in the US and a parallel unit in the UK and Commonwealth. Sixteen ounces make a pound; in the UK and Ireland, fourteen pounds make a stone, used almost exclusively for body weight. The US ton is 2,000 lbs (about 907.18 kg); the UK 'long ton' is 2,240 lbs (about 1,016.05 kg); the metric tonne is 1,000 kg (about 2,204.62 lbs). Three different 'tons' to keep straight when reading specs.
Two specialty pound systems still appear in niche contexts. Troy pounds (about 0.373 kg) are used for precious metals. When you see gold or silver quoted 'per ounce,' that's typically a troy ounce of about 31.1 grams, not the avoirdupois ounce of 28.35 grams. Apothecaries' pounds appear only in older pharmacy or chemistry texts.
| From | Equivalent |
|---|---|
| 1 kilogram | 2.20462 pounds, 35.274 oz |
| 1 pound | 0.453592 kg, 453.592 grams (exact) |
| 1 ounce (avdp) | 28.3495 grams |
| 1 troy ounce | 31.1035 grams (precious metals) |
| 1 stone (UK) | 6.35029 kg, 14 lbs |
| 1 US ton | 907.185 kg, 2,000 lbs |
| 1 metric tonne | 1,000 kg, 2,204.62 lbs |
| 1 gram | 0.035274 oz, 0.00220462 lbs |
Mass measures the amount of matter; weight measures the gravitational force on that matter. In everyday usage they're treated the same, and conversion between pounds and kilograms works correctly either way.
Yes. 1 international avoirdupois pound is defined as exactly 0.45359237 kg, so 1 kg equals 2.20462 lbs accurate to six significant figures.
Troy weight is a separate historical system used for precious metals. A troy ounce is about 31.1 grams; a standard (avoirdupois) ounce is 28.35 grams. Gold, silver, and platinum prices are quoted per troy ounce.
70 kg is 154.32 pounds. The exact conversion factor is 2.20462 lbs per kg.
1 metric tonne equals 1,000 kg or about 2,204.62 lbs. That's about 10% heavier than a US 'short ton' (2,000 lbs).
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