Understanding weight
The math, made plain.
A note on words: in everyday speech "weight" means mass. Strictly, weight is force; mass is the stuff being weighed. The converter, like most of the world, treats them as one.
The metric ladder.
Metric weight is built from the gram. Each step up the ladder multiplies by a thousand: a kilogram is a thousand grams, a tonne is a thousand kilograms, a milligram is a thousandth of a gram. Three jumps cover the whole human-scale range from a grain of sugar to a small car.
1 g = 1000 mg · 1 kg = 1000 g · 1 t = 1 000 000 g
The imperial set.
Imperial weights are more eclectic. Sixteen ounces make a pound; fourteen pounds make a stone; the larger units (the long ton, the short ton, the hundredweight) differ from country to country and aren't worth committing to memory unless you're shipping freight. For everyday work, ounces, pounds, and stone are enough.
1 lb = 16 oz · 1 st = 14 lb = 224 oz
Where metric meets imperial.
The same 1959 treaty that fixed the inch fixed the pound. By international agreement, one pound is exactly 0.45359237 kilograms — not approximately, exactly. Every other cross-system weight conversion in use today derives from that one definition.
1 pound ≡ 0.45359237 kg
Derived bridges
- 1 ounce = 28.349523125 g
- 1 stone = 6.35029318 kg
- 1 short ton (US) = 907.18474 kg
- 1 long ton (UK) = 1016.0469088 kg
Three worked conversions.
The same rule of thumb applies as for length: if you're going from a larger unit to a smaller one, multiply; from smaller to larger, divide.
70 kilograms to pounds
1 pound = 0.45359237 kg
A kilogram is bigger than a pound, so the count grows — divide by the factor.
70 ÷ 0.45359237 ≈ 154.3236
= 154.3236 lb
200 pounds to kilograms
1 pound = 0.45359237 kg
Going the other way: pounds are smaller than kilograms, so the count shrinks — multiply by the factor.
200 × 0.45359237 ≈ 90.7185
= 90.7185 kg
8 ounces to grams
1 ounce = 28.349523125 g
An ounce is larger than a gram, so the count grows — multiply.
8 × 28.349523125 ≈ 226.7962
= 226.7962 g
A note on precision.
Every conversion above runs in your browser using IEEE 754 double-precision arithmetic — accurate to about fifteen significant digits. For most kitchens that's overkill; for a jeweller, it's exact; for an analytical chemist, the published bridges are authoritative.
Read next