What this tool does
This converter moves between kilograms, pounds, and stone + pounds in any of the six directions. Type a value, pick a conversion pair from the dropdown, and the result appears immediately in your browser — nothing is sent to a server.
Stone + pounds is the standard way body weight is expressed in the UK: a person weighs, say, 11 st 3 lb rather than 157 lb or 71.2 kg. The tool always breaks stone-and-pound output into the integer stone count and the remaining decimal pounds, matching what a GP or pharmacy printout shows.
The conversions
One kilogram is defined as 1 000 g in the International System of Units. The pound is defined by the 1959 international agreement as exactly 0.453 592 37 kg, which makes 1 kg = 1 ∕ 0.453 592 37 ≈ 2.20462262185 lb. The stone is exactly 14 lb by UK statute.
To convert stone + lb to kilograms, first convert the whole value to pounds (stone × 14 + lb) and then multiply by 0.453 592 37.
Worked example
Take 70 kg, a typical adult body weight. Multiplying by 2.20462262185 gives 70 × 2.20462262185 = 154.3236 lb. Dividing the pound value by 14 and taking the integer part gives 11 st, with 154.3236 − (11 × 14) = 0.3236 lb remaining. So 70 kg = 11 st 0.3236 lb.
Why stone for body weight?
The stone as a unit of trade dates to medieval England, where it was used for wool, meat, and butter. Parliament standardised it at 14 lb in the Weights and Measures Act 1835. Although the UK officially adopted metric for most trade after the Weights and Measures Act 1985, body weight in stone remained in everyday use — it is still the default on bathroom scales sold in the UK and is the unit NHS patient records typically display alongside metric figures.
Pounds alone (without stone) remain standard for body weight in the United States and in most clinical contexts there, while continental Europe uses kilograms exclusively.
Common uses
- Body weight: checking a kg figure from a GP, scales, or a fitness app against the stone + lb reading most UK adults think in.
- Luggage: airline allowances are often quoted in kilograms; US carriers may use pounds.
- Recipes and food labels: older British recipes quote ingredients in pounds and ounces; modern packaging uses grams.
- Gym equipment: weight plates are marked in both kg and lb depending on country of manufacture.
Frequently asked
How many pounds are in a stone?
Exactly 14 lb. One stone = 14 lb is a statutory definition, not an approximation, so all stone–pound conversions are exact with no rounding involved.
Is the pound-to-kg conversion exact?
Yes. The 1959 international yard and pound agreement fixed 1 lb = 0.453 592 37 kg precisely. The reciprocal (1 kg ≈ 2.20462262185 lb) is a repeating decimal, so the converter rounds to 4 decimal places.
What does "11 st 0 lb" look like in pounds?
11 × 14 = 154 lb exactly. Choose the st + lb → lb pair and enter 11 st and 0 lb to confirm.