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Weight converter

Convert milligrams, grams, kilograms, tonnes, ounces, pounds and stone, with stone and pounds worked out for body weight and the US and UK tons kept apart.

The weight you have

All three tons are listed separately, because they are three different weights: 2,000 lb in the US, 2,240 lb in the UK and 1,000 kg as a tonne.

Converted

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Enter a weight and pick the two units.

A pound is exactly 0.45359237 kilograms

That is a definition, not a measurement. The international yard and pound agreement of 1959 fixed it, and every other imperial weight follows by whole number multiplication:

  • 1 ounce = a sixteenth of a pound = exactly 28.349523125 g
  • 1 stone = 14 pounds = exactly 6.35029318 kg
  • 1 US short ton = 2,000 pounds = exactly 907.18474 kg
  • 1 UK long ton = 2,240 pounds = exactly 1,016.0469088 kg

So the figures this tool prints are exact as far as they go. The familiar shorthand, 2.2 pounds to a kilogram, is short by about a fifth of a percent, which is half a pound on an adult and worth knowing if you are tracking a change rather than a total.

The three tons

This is the conversion that goes wrong most often, because all three are written “ton” and they are close enough for the mistake to survive a glance.

  • Short ton, 2,000 lb, about 907 kg. What “ton” means in the United States.
  • Long ton, 2,240 lb, about 1,016 kg. The imperial ton, still used in shipping.
  • Tonne, exactly 1,000 kg, sometimes written “metric ton”.

A long ton is 12% heavier than a short one. On a single load that is a rounding error you might not notice; on a shipment it is a difference somebody pays for. All three are listed separately here so there is nothing to guess.

Stone, pounds, and why the decimal is no use

A stone is 14 pounds, and it is used for body weight in Britain and Ireland and essentially nowhere else. Converting 70 kg gives 11.02 stone, which is correct and not how the number is ever said. What people say is eleven stone and a bit, so the tool works out the pounds left over as well.

In the United States the same weight is given in pounds alone: 154 lb. Babies and parcels get pounds and ounces, so 3.4 kg is 7 lb 8 oz, which is why this tool shows that reading too.

Weight, mass, and the ounce that is not an ounce

Strictly, mass is how much matter something contains and weight is the force gravity pulls it with. Kilograms and pounds as used on any scale are measures of mass, and that is what is converted here. The everyday word for it is weight, which is what this page is called.

Two ounces are worth keeping apart. The troy ounce, used only for gold and silver, is about 31.1 g rather than 28.35 g, so a troy ounce is roughly 10% heavier. A fluid ounce measures volume rather than weight, and shares the name only because a fluid ounce of water happens to weigh about an ounce. For anything denser or lighter than water they part company immediately.

Questions

How many pounds are in a kilogram?
2.2046226218, and the digits after that are real too. A pound is defined as exactly 0.45359237 kilograms, so the conversion is exact rather than measured. The 2.2 everyone remembers is under by about a fifth of a percent, which is fine for a rough answer and about half a pound out on a person.
How do I convert my weight to stone and pounds?
Enter it in kilograms and read the 'in stone and pounds' line. A stone is exactly 14 pounds, so the plain conversion gives a decimal like 11.02 stone, which nobody says. The tool splits it into 11 stone and the pounds left over.
Is a ton the same everywhere?
No, and this is the one that catches people out. A US short ton is 2,000 pounds, about 907 kg. A UK long ton is 2,240 pounds, about 1,016 kg. A metric tonne is exactly 1,000 kg. The three are within about 12% of each other, which is close enough to look like a rounding difference and far enough to matter on a shipping invoice. All three are listed separately here so you never have to guess which one was meant.
What is the difference between weight and mass?
Mass is how much matter something contains. Weight is the force gravity pulls it with, which depends on where you are: the same body is about a sixth as heavy on the moon while its mass has not changed. Kilograms and pounds as used on a scale are both measures of mass, and that is what this tool converts. The everyday word for it is weight, which is why the page is called what it is.
How many ounces are in a pound?
Sixteen, and it is exact. That is the avoirdupois ounce, which is the one used for food, parcels and people. A troy ounce, used only for precious metals, is different and heavier at about 31.1 grams against 28.35. This tool uses the ordinary ounce.
Why is a fluid ounce not the same as an ounce?
Because one measures weight and the other measures volume. They share a name because a fluid ounce of water weighs roughly an ounce, which is a historical convenience rather than a rule. For anything that is not water the two come apart quickly: a fluid ounce of honey weighs about half as much again. Use the unit converter's volume category for fluid ounces.
Which countries still use stone?
Britain and Ireland, and almost only for body weight. A British doctor will record kilograms and a British person will say stone. It is not used in the United States, where the same weight is given in pounds alone, so 11 stone is 154 pounds.
Does anything I type here get sent anywhere?
No. The conversion runs in your browser, in the page you are already looking at. Nothing is uploaded, stored or logged, and closing the tab clears it. You can disconnect from the internet and the tool will keep working.

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