Weight converter
Convert between weight units.
Weight Guide
Kilograms and Pounds
Kilogram (kg) is the basic mass unit in the metric system. Pounds (lb) are used mainly in the USA and UK. 1 kg = 2.20462 pounds. Body weight is given in kilograms in metric countries and in pounds in the USA (e.g., 150 lb = 68 kg). Stone (st) = 6.35 kg is still used in the UK for body weight.
Kitchen Weights
Polish cooking recipes use grams (g) and milliliters (ml). American recipes use cups (236 ml), tbsp (15 ml), tsp (5 ml), oz (fluid ounce = 30 ml). British cup is 284 ml. When converting recipes: 1 cup flour ≈ 125 g, 1 cup sugar ≈ 200 g.
International Cooking Recipes
Italian and French cuisine uses grams. British cuisine uses cups, tablespoons, teaspoons. American cuisine uses cups and ounces. When buying cookbooks from abroad, check the measurement system. Kitchen scales often have unit switching functions kg/lb, g/oz, ml/fl oz.
The troy ounce is heavier than the kitchen ounce — but the troy pound is lighter
Precious metals are weighed on a different system from food. A troy ounce is 9.71% heavier than the ordinary avoirdupois ounce, yet a troy pound is lighter than an ordinary pound, because it contains twelve ounces rather than sixteen. Both facts are true at once, and that is exactly why the two systems get mixed up.
How it works
- Converts between metric mass units and both imperial systems — avoirdupois for everyday weight, troy for precious metals.
- Keeps the two ounce definitions distinct instead of collapsing them into one 'ounce'.
- Handles the stone, still in everyday use for body weight in Britain and Ireland.
avoirdupois ounce = 28.349523125 g food, post, body weight troy ounce = 31.1034768 g gold, silver, platinum avoirdupois pound = 16 oz = 453.59 g troy pound = 12 oz = 373.24 g heavier ounce, fewer of them, lighter pound
Worked example
Pricing a kilogram of gold at 2,000 per ounce, using each definition.
- 1 kg ÷ 31.1035 g = 32.15 troy ounces → 64,301
- 1 kg ÷ 28.3495 g = 35.27 ordinary ounces → 70,548
- the same kilogram, the same quoted price
- difference: 6,246
Using the wrong ounce overstates the value by 6,246 on a single kilogram — roughly 9.7%. Bullion is always quoted in troy ounces, so an ordinary-ounce conversion inflates every figure it touches.
Reading the result
- The apparent contradiction resolves cleanly: troy weighs each ounce more but puts fewer in a pound. 12 × 31.10 = 373 g against 16 × 28.35 = 454 g, so the troy pound is 82.3% of the everyday one.
- Only precious metals and gemstones use troy. Food, freight, postage and body weight are all avoirdupois — so 'ounce' in a recipe and 'ounce' in a gold price are different quantities sharing a word.
- A stone is 14 avoirdupois pounds, or 6.35 kg. It remains standard for body weight in the UK and Ireland and is essentially unused elsewhere, which makes it a common source of confusion in health data.
- Strictly these are units of mass, not weight — mass is unchanged by location, weight is not. The distinction rarely matters on Earth's surface, but it is why scientific work says 'mass' and shop scales say 'weight'.
Common questions
- Why do precious metals use a different ounce?
- The troy system predates avoirdupois and stayed in use for bullion and coinage because contracts, exchanges and refiners were all built around it. Changing would have invalidated centuries of standing agreements for no practical gain.
- How can a heavier ounce make a lighter pound?
- Because the two systems disagree about how many ounces a pound holds. Troy uses twelve, avoirdupois sixteen. The 9.71% heavier ounce cannot make up for having four fewer of them, so the troy pound lands 17.7% lighter.