Utiliki

Weight & Mass Converters

42 converters, all running in your browser.

The kilogram is the SI base unit of mass, and since 2019 it has been defined by fixing the Planck constant rather than by a platinum-iridium cylinder in a vault near Paris. That change made no practical difference to any conversion here; it made the definition reproducible in any properly equipped laboratory.

Strictly, these are mass conversions rather than weight conversions. Mass is how much matter something contains and does not change; weight is the force gravity exerts on it and varies with location. A 70 kg person has the same mass on the Moon and about one sixth of the weight. In everyday use the two words are interchangeable, and every unit here is a mass unit.

The pound was fixed at exactly 0.45359237 kg by the same 1959 agreement that redefined the inch, so pound-to-kilogram conversions are exact. The stone, still used for body weight in the UK and Ireland, is exactly 14 pounds.

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Conversion factors

FromToMultiply by
KilogramsGrams1000
KilogramsMilligrams1000000
KilogramsPounds2.2046226
KilogramsOunces35.273962
KilogramsStone0.15747304
GramsKilograms0.001
GramsMilligrams1000
GramsPounds0.0022046226
GramsOunces0.035273962
GramsStone1.5747e-4
MilligramsKilograms1.0000e-6
MilligramsGrams0.001
MilligramsPounds2.2046e-6
MilligramsOunces3.5274e-5
MilligramsStone1.5747e-7
PoundsKilograms0.45359237
PoundsGrams453.59237
PoundsMilligrams453592.37
PoundsOunces16
PoundsStone0.071428571

Where Weight Conversions Go Wrong

The recurring error in cooking is converting between mass and volume without a density. Flour and water are both measured in cups and a cup of each weighs very differently — about 120 g for flour, 240 g for water. No unit converter can bridge that gap, because the answer depends on the substance and, for flour, on whether it was scooped or spooned.

The recurring error in shipping is confusing the ton. A metric 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. Three units, one word, an 11% spread — and freight quotes routinely fail to say which.

Body Weight Conventions

The UK and Ireland quote body weight in stones and pounds, written "11 st 4 lb" rather than as a decimal. Converting 158 pounds gives 11.29 stone, which nobody says: the correct reading is 11 stone 4 pounds, taking the whole part and multiplying the remainder by 14.

The US quotes pounds alone; most of the rest of the world uses kilograms. A useful anchor is that 70 kg is about 11 stone or 154 pounds.

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