How the conversion works
All five units on this page hang off one exact definition: since 1959 the avoirdupois pound has been exactly 0.45359237 kg. Divide by 16 and you get the ounce; multiply by 14 and you get the stone. Because everything is pinned to the kilogram, converting between any pair of units is exact multiplication, with rounding only at the display stage.
The tool converts your value into grams first, then out into every other unit. Type 500 in grams and you instantly get the same weight as kilograms, ounces, pounds and stones, no button pressing required.
Worked examples
Quick reference
- 1 oz ≈ 28.35 g, and 100 g ≈ 3.53 oz
- 1 lb ≈ 453.6 g, just under half a kilogram
- 1 kg ≈ 2.2046 lb ≈ 35.27 oz
- 1 st = 14 lb ≈ 6.35 kg
- A bag of sugar (1 kg) ≈ 2 lb 3 oz
- A pound of butter is a little over 450 g
Which unit for which job
British life splits weight by context. Recipes written in the last few decades use grams; older ones, and most American ones, use ounces and pounds. Body weight is spoken in stones and pounds but recorded by the NHS in kilograms. Supermarkets price per kilogram by law, yet market stalls still happily quote per pound. This converter bridges all of it, and if the recipe in front of you measures in cups rather than weight, our cups to grams converter handles that separate problem.
For mental maths, two approximations cover most situations: an ounce is "about 28 g" and a kilogram is "about 2.2 lb". If you are specifically converting body weight, the kg to stone converter presents the answer as stones and pounds, the way British scales and doctors' letters actually phrase it, rather than as decimal stones.
One trap to know about: the troy ounce. Gold, silver and other precious metals are weighed in troy ounces of about 31.103 g, roughly 10% heavier than the everyday avoirdupois ounce this page uses. A "one ounce" gold coin therefore weighs more than an ounce of flour. Bullion is the only place you are likely to meet the troy system, but if a price per ounce looks odd, that is usually why.
A note on precision: this tool keeps six significant figures, but your scales will not. Kitchen scales typically resolve to 1 g and bathroom scales to 0.1 kg, so when you convert a recipe, rounding 17.64 oz to "a little over 17 and a half ounces" or 907.18 g to 907 g loses nothing you could actually measure. The exact figures matter more when you are converting prices per unit weight, where small errors multiply.
Frequently asked questions
How many grams are in an ounce?
Exactly 28.349523125 g. That comes straight from the definition of the pound (453.59237 g) divided by 16. For kitchen purposes, 28.35 g per ounce is accurate to a hundredth of a gram.
How do I convert kilograms to pounds?
Multiply by about 2.20462. So 5 kg is 11.02 lb and 70 kg is 154.3 lb. Going the other way, multiply pounds by 0.45359237 to get kilograms.
How many pounds are in a stone?
14 pounds, which makes a stone exactly 6.35029318 kg. Body weight in the UK is usually quoted in stones and pounds, so 11 stone 11 lb is 165 lb, or about 74.8 kg.
Is a UK ounce the same as a US ounce?
For weight, yes. Both countries use the avoirdupois ounce of 28.349523125 g. The confusion comes from fluid ounces, which measure volume and do differ: a UK fluid ounce is 28.41 mL and a US one is 29.57 mL.
How accurate are the results?
The tool converts through grams using the exact definition 1 lb = 0.45359237 kg and only rounds for display, to six significant figures. Kitchen and bathroom scales round far more aggressively than that.