Weight converter
Nine units of mass at once: milligrams, grams, kilograms, tonnes, ounces, pounds, stone, US tons and UK tons. The pound is exactly 0.45359237 kilograms by definition, so every imperial figure here follows exactly from the metric one and none of them is a rounded constant.
How to convert weight
The word "ton" is three different quantities and the table lists all three rather than choosing for you. A US short ton is 2,000 pounds, which is 907.18 kg. A UK long ton is 2,240 pounds, which is 1,016.05 kg. A metric tonne is 1,000 kg, about 2,204.6 pounds, so it sits between the two and is about one and a half per cent lighter than the long ton. On a shipping quote, a freight rate or a vehicle load limit, the difference between the short ton and the tonne is around ten per cent, which is enough to matter and small enough to go unnoticed.
Stone is the other reliable source of error. One stone is fourteen pounds, about 6.35 kg, and it is still how body weight is normally given in Britain and Ireland. It is always spoken and written as two numbers: 11 stone 4 means eleven stone and four pounds, which is 158 pounds or 71.7 kg. Typing that as 11.4 stone gives 159.6 pounds instead, and the error grows with the pounds part. Convert the stone, then add the pounds.
Mass and weight are not the same thing, though everyday language treats them as one. Mass is how much matter something is, weight is the force gravity exerts on it, and a kilogram is a unit of mass while a pound is used for both. Everything in this table converts mass, which is what a scale is calibrated to report and what a shipping document means. The distinction only bites in physics, in aviation load sheets and in the rare case of a scale calibrated for a different latitude.
Four units people look for are not here, on purpose. The troy ounce and the troy pound belong to precious metals and are a separate system that shares a name with this one, which is exactly why keeping them in the same dropdown causes losses. The carat, at 200 mg exactly, belongs to gemstones. The grain, at 64.79891 mg, survives in ammunition and pharmacy. Mixing any of them into a table with kilograms invites the wrong row to be picked, and the ounce is the one where it would cost real money.
What people use it for
- Working out which ton a shipping quote means
- Converting a body weight given in stone and pounds
- Reading a load limit in tonnes against one in short tons
- Turning a recipe's grams into ounces and back
- Checking a parcel against a courier's weight bracket in the other system
- Comparing a US and a UK spec sheet that both say "ton"
Questions
About 2.20462. The exact definition runs the other way: a pound is exactly 0.45359237 kg.
No. A US short ton is 2,000 lb, a UK long ton is 2,240 lb, and a metric tonne is 1,000 kg. All three are separate rows here.
About ten per cent. A tonne is 2,204.6 lb against the short ton's 2,000, which is enough to matter on a freight rate and small enough to slip past.
Usually the metric tonne outside North America and the short ton inside it, but the document should say. If it says only "ton", ask.
Fourteen pounds, about 6.35 kg. It is still the everyday unit for body weight in Britain and Ireland.
No. It means eleven stone and four pounds, 158 lb or 71.7 kg. Read as a decimal it comes out 1.6 lb heavier.
Not strictly. Weight is a force and depends on gravity; mass does not. Everyday use conflates them, and everything converted here is mass.
Exactly 28.349523125, which follows from the pound being exactly 0.45359237 kg and the ounce being a sixteenth of it.
No, deliberately. It is 31.1034768 g against the everyday ounce's 28.35, and having both in one dropdown is how a gold weight gets converted with the wrong row.
Not here. A metric carat is 200 mg exactly, so a five-carat stone is one gram; multiply carats by 0.2 to get grams.
Not in this table either. A grain is 64.79891 mg exactly, and 7,000 of them make a pound. It is still used for bullets and for some medicine doses.
Because the 1959 international agreement defined the pound as an exact number of kilograms. Every unit above is a whole multiple or fraction of that, so no rounded constant is involved.
0.45359237, exactly. That figure is the definition rather than a measurement.
Divide the kilograms by 6.35029318 for the stone, keep the whole number, then multiply what is left over by 14 for the pounds.
Yes. Once a result drops below a millionth or climbs past a billion, in whatever unit you are reading, the display switches to exponential form rather than printing a row of zeros.
They share a base unit, so one multiplication converts between them. It is a nine-orders-of-magnitude jump — a tonne is a thousand million milligrams — which is what the exponential display is for, and one tonne is exactly where it kicks in.
In this table, no: everything here is mass. Pound-force is the weight of one pound of mass at standard gravity, and it belongs in a force conversion rather than a mass one.
No. Every row is one multiplication and it happens in this page.