Weight Converter

How to use the Weight Converter

1. Enter the weight you want to convert, such as 70 or 2.5.
2. Pick the unit you have in From and the unit you need in To. Use the swap button to flip the direction.
3. Read the result, plus a pounds-and-ounces or stones-and-pounds version when you convert to those units.
4. Check the list below for the same weight in all 14 units and click any value to copy it.

Features

• Exact factors: 1 lb = 0.45359237 kg, 1 troy oz = 31.1034768 g
• Pounds-and-ounces and stones-and-pounds breakdowns
• Precious-metal units: troy ounce, carat, grain and tola
• US short tons, British long tons and metric tonnes kept apart
• Every unit at once, with one-click copy
• Choose automatic precision or fixed decimal places

Mass, weight and the kilogram

Strictly speaking, kilograms and pounds measure mass, the amount of matter in an object, while weight is the force gravity puts on that mass. In everyday life the two words mean the same thing, and a bathroom scale or kitchen scale reports mass. That is why you can convert “weight” in kilograms to pounds with a single fixed factor anywhere on Earth.

For 130 years the kilogram was defined by a single platinum-iridium cylinder kept in a vault near Paris. In 2019 that artifact was retired and the kilogram was redefined through a fixed value of the Planck constant, so it can now be realized in any well-equipped laboratory. The pound follows the kilogram: since the 1959 international agreement, one avoirdupois pound is exactly 0.45359237 kg, and one ounce is exactly 1/16 of that, or 28.349523125 g.

Avoirdupois, troy and tola

The ounces and pounds used for food and body weight belong to the avoirdupois system. Gold, silver and platinum are priced in troy ounces, which are heavier: 31.1034768 g instead of 28.35 g. Quoting a gold price “per ounce” almost always means per troy ounce, so mixing the two up undervalues metal by about 10%.

In Pakistan, India, Nepal and the Gulf, gold is also traded by the tola. One tola is 180 grains, which works out to exactly 11.6638038 g, or 3/8 of a troy ounce. The popular ten-tola bar therefore weighs about 116.64 g. Gemstones use the metric carat of exactly 200 mg; do not confuse it with the karat that describes gold purity.

Stones, tons and tonnes

In the UK and Ireland, body weight is still often given in stones of 14 pounds. Heavy loads come in three different “tons”: the US short ton of 2,000 lb (907.18 kg), the British long ton of 2,240 lb (1,016.05 kg) and the metric tonne of 1,000 kg. Shipping quotes and engineering specifications sometimes just say “ton”, so check which one is meant.

Worked examples

Body weight: 70 kg

Divide by 0.45359237: 70 ÷ 0.45359237 = 154.32 lb. The fraction 0.32 lb × 16 = 5.2 oz, so that is 154 lb 5 oz, or 11 st 0.3 lb.

Baking: 250 g of butter in ounces

Divide grams by 28.349523125: 250 ÷ 28.3495 = 8.82 oz, a little more than two US sticks of butter.

Gold: 1 kg bar in troy ounces

1,000 ÷ 31.1034768 = 32.15 troy ounces, or 85.74 tola.

Reference table

For recipes that list ingredients in cups, a weight converter is not enough because a cup of flour and a cup of sugar weigh different amounts. Use the Cooking Converter, which knows typical ingredient densities.

Frequently asked questions