Weight Converter

How the converter works

Each unit is held as an exact number of kilograms. The value is multiplied by the source unit's mass in kilograms and divided by the target unit's mass. Because the avoirdupois pound is defined as exactly 0.45359237 kg, every customary unit derived from it — the ounce (1/16 lb), the stone (14 lb), the short ton (2,000 lb) and the long ton (2,240 lb) — is also an exact decimal.

result = value × (kg per source unit) ÷ (kg per target unit)

Worked examples

Example 1: 150 lb in kilograms

150 × 0.45359237 = 68.0388555 kg, about 68.04 kg.

Example 2: 250 g of flour in ounces

0.25 kg ÷ 0.028349523125 = 8.818490 oz, just under half a pound.

Example 3: 11 st 6 lb in kilograms

11 stone is 154 lb; add 6 to get 160 lb. 160 × 0.45359237 = 72.5747792 kg.

Example 4: a 3.5-tonne vehicle limit in US tons

3,500 kg ÷ 907.18474 = 3.858090 short tons, or 3.444723 long tons.

How to read the result

The large figure is the mass in your chosen target unit. The formula line shows the one multiplier between the two units, which you can reuse. The table lists the mass in all nine units, with the target row highlighted, so you can read off grams and ounces for a recipe or tonnes and tons for freight at the same time. Up to six decimals are shown.

Mass versus weight

Strictly, kilograms and pounds measure mass — the amount of matter — while weight is the force gravity exerts on it, measured in newtons or pounds-force. In everyday use and on bathroom scales, "weight" means mass, and the numbers are the same anywhere on Earth. This converter deals with mass in that everyday sense. If you need force, multiply the mass in kilograms by the local gravitational acceleration (about 9.80665 m/s² standard) to get newtons.

Which ounce, which ton?

Several units share names. The ounce used here is the avoirdupois ounce for food and parcels. Gold, silver and gemstones use the troy ounce of 31.1034768 g, about 10% heavier, and liquids use the fluid ounce, a unit of volume rather than mass. "Ton" can mean the metric tonne of 1,000 kg, the US short ton of 2,000 lb or the UK long ton of 2,240 lb; the difference between the smallest and largest is about 12%. Shipping documents and specifications should state which is meant — if they do not, ask.

Common uses

People convert body weight between pounds, kilograms and stone; baby weights between grams and pounds-and-ounces; baggage allowances between kilograms and pounds; recipe quantities between grams and ounces; and freight, vehicle and bridge limits between tonnes and tons. Fitness programmes often switch between kilogram plates and pound plates. For the single most common conversion, the kg to lbs converter adds pounds-and-ounces and stone breakdowns and a reference table.

Limits and good practice

Kitchen and bathroom scales are typically accurate to a gram or a tenth of a pound at best, so round the result to match. Medication doses based on body weight must use the unit your prescriber specifies; never convert a dose yourself without checking. Precious-metal prices quoted per troy ounce cannot be converted with this tool's avoirdupois ounce. For distances, try the length converter, and for oven or weather temperatures the temperature converter.

Converting mixed units such as pounds and ounces

Customary weights are often written in two parts: 7 lb 8 oz for a newborn, or 12 st 3 lb for an adult. Convert both parts to a single unit before using the converter. Ounces to pounds is a division by 16, so 7 lb 8 oz is 7.5 lb, and 7.5 lb converts to 3.4019 kg. For stone, multiply by 14 and add the pounds: 12 st 3 lb is 171 lb, or 77.5643 kg. Going the other way, convert to pounds, keep the whole number, and multiply the decimal part by 16 to get ounces. The kg to lbs page performs this split automatically for every result, and also shows stone and pounds once a weight reaches 14 lb or more, so you can skip the manual step entirely.