⚖️ Weight Converter

What is the Weight Converter?

Most of the world measures mass with the metric system, where the base unit is the kilogram (kg). Smaller masses are given in grams (1 kg = 1000 g) or milligrams (1 g = 1000 mg), and larger ones in tonnes (1 tonne = 1000 kg). The imperial and US customary systems use the pound (lb), which splits into 16 ounces (oz), and in the UK the stone (1 stone = 14 lb) is still common for body weight. These two families do not line up neatly, which is why a converter is handy.

The cleanest way to convert is to route everything through the kilogram, because the pound has an exact legal definition in terms of it: 1 lb = 0.45359237 kg exactly. From that single anchor, every other factor follows. To turn pounds into kilograms you multiply by 0.45359237, and to go the other way you divide (or multiply by its reciprocal, 2.2046226). Grams, tonnes, ounces and stone are then just fixed multiples of the kilogram or the pound, so the tool converts your input to kilograms first and then out to the unit you want.

Different countries lean on different units, so a quick converter removes a lot of friction. The United States uses pounds and ounces for almost everything, from groceries to body weight to shipping. The United Kingdom runs a hybrid: stone and pounds for personal weight, but kilograms and grams in shops and recipes. Most other countries are fully metric. That mismatch is exactly why a recipe might list flour in grams while a scale reads in ounces, or why a gym programme written in kilograms meets a plate marked in pounds.

Watch out for the word ton, which has three different meanings. The metric tonne is 1000 kg (about 2,204.6 lb). The US short ton is 2,000 lb (about 907 kg), and the UK long ton is 2,240 lb (about 1,016 kg). They are close but not equal, so for freight, vehicles or commodities it pays to confirm which ton is meant. There is also a separate ounce for precious metals: the troy ounce (about 31.103 g) used for gold and silver is heavier than the everyday avoirdupois ounce (about 28.35 g), so never use one in place of the other when pricing bullion.

A quick note on wording: in everyday use people say weight when they really mean mass. Mass is the amount of matter in an object and stays the same everywhere, while weight is the force gravity exerts on that mass and changes with location (you would weigh less on the Moon). The kilogram and pound used here are units of mass. Bathroom scales report mass even though we call the reading weight, so for day to day purposes the distinction rarely matters, but it is worth knowing when a question is really about force (measured in newtons).

When to use it

• Converting a recipe that lists ingredients in grams and ounces.
• Reading your body weight in kg when scales or forms expect pounds or stone.
• Checking baggage or parcel limits quoted in kg against a scale that reads in pounds.
• Logging gym or barbell loads where plates are marked in kg but a program is written in lb.
• Recording a baby or pet weight in pounds and ounces from a kilogram reading.
• Estimating shipping or freight charges where weights are billed in kilograms or tonnes.

How to use the Weight Converter

1. Type the amount you know into its matching field (for example kilograms).
2. Read the converted value in the unit you need (pounds, ounces, stone, grams or tonnes).
3. For body weight, note the stone-and-pounds breakdown where shown.
4. Switch the value in any field and every other unit recalculates at once.

Formula & method

Worked examples

Exact mass conversion factors

Body weight: kilograms to stone and pounds

Common mistakes to avoid

• Confusing pounds and ounces. There are 16 ounces in a pound, not 100. A reading of 5 lb 8 oz is 5.5 lb, not 5.08 lb.
• Mixing mass and force. Pounds and kilograms here are units of mass. Force is measured in newtons (or pounds-force), so do not equate a kg reading with a newton value.
• Rounding kg to exactly 2.2 lb. The factor is 2.2046226, not 2.2. The shortcut adds roughly 0.2% of error, which grows noticeable on heavy loads.
• Confusing troy and avoirdupois ounces. Gold and silver are priced per troy ounce (31.103 g), which is heavier than the everyday avoirdupois ounce (28.35 g). Using the wrong one misvalues bullion by about 10 percent.
• Assuming a ton is always 1000 kg. The metric tonne is 1000 kg, but a US short ton is 907 kg and a UK long ton is 1,016 kg. Check which ton a figure means before converting.
• Reading stone-and-pounds as a decimal. A weight of 11 st 6 lb is not 11.6 stone. The pounds are out of 14, so 11 st 6 lb is about 11.43 stone. Convert the pounds to a fraction of a stone first.

Glossary

Kilogram (kg)

The base SI unit of mass, equal to 1000 grams.

Pound (lb)

An imperial and US customary unit of mass, defined as exactly 0.45359237 kg.

Ounce (oz)

A sixteenth of a pound, about 28.35 grams. Properly the avoirdupois ounce.

Troy ounce

A unit of about 31.103 grams used for precious metals such as gold and silver, heavier than the everyday ounce.

Stone

A UK unit of mass equal to 14 pounds (about 6.35 kg), used mainly for body weight.

Tonne (t)

A metric unit equal to 1000 kilograms, also called a metric ton.

Short ton / long ton

The US short ton is 2,000 lb (about 907 kg); the UK long ton is 2,240 lb (about 1,016 kg).

Mass vs weight

Mass is the amount of matter (constant everywhere); weight is the gravitational force on that mass and varies with location.

Frequently asked questions