Ask someone in Britain how much they weigh and you will probably hear "eleven stone four", not "72 kilos" or "158 pounds". Doctors and the NHS record weight in kilograms, recipes and shops use grams, and American friends think in pounds. If you move between the UK, Ireland, the US, Canada and the Netherlands, you need all three.
The exact relationship
The stone is defined in pounds, and the pound has been defined in kilograms since the 1959 international yard and pound agreement:
| Unit | Equals |
|---|---|
| 1 stone (st) | 14 pounds (lb), exactly |
| 1 pound (lb) | 0.45359237 kilograms, exactly |
| 1 stone | 6.35029318 kilograms, exactly |
| 1 kilogram | about 2.2046 pounds, or 0.1575 stone |
Because both definitions are exact, any conversion between stone, pounds and kilograms can be done without rounding until the last step.
How to convert stone and pounds to kilograms
- Multiply the stone by 14 to get pounds.
- Add the remaining pounds.
- Multiply the total by 0.45359237.
Worked example: 11 st 4 lb = (11 × 14) + 4 = 158 lb. Then 158 × 0.45359237 = 71.67 kg.
For a quick mental estimate, 1 stone is a little over 6⅓ kg, so 11 stone is about 70 kg.
How to convert kilograms to stone and pounds
- Divide the kilograms by 6.35029318. The whole number is the stone.
- Multiply the decimal part by 14 to get the remaining pounds.
Worked example: 80 kg ÷ 6.35029318 = 12.598 stone. The decimal part, 0.598 × 14 = 8.4 lb, so 80 kg is about 12 st 8 lb.
Warning: a common mistake is to read 12.6 stone as "12 stone 6 pounds". It is not: 0.6 of a stone is 8.4 pounds, because a stone has 14 pounds, not 10.
Stone to kg and lbs chart
| Stone | Kilograms | Pounds |
|---|---|---|
| 8 st | 50.8 kg | 112 lb |
| 9 st | 57.2 kg | 126 lb |
| 10 st | 63.5 kg | 140 lb |
| 11 st | 69.9 kg | 154 lb |
| 12 st | 76.2 kg | 168 lb |
| 13 st | 82.6 kg | 182 lb |
| 14 st | 88.9 kg | 196 lb |
| 15 st | 95.3 kg | 210 lb |
| 16 st | 101.6 kg | 224 lb |
| 17 st | 108.0 kg | 238 lb |
| 18 st | 114.3 kg | 252 lb |
| 20 st | 127.0 kg | 280 lb |
Who still uses the stone?
The stone is used informally for body weight in the UK and Ireland. It is no longer used for trade: goods are sold by the kilogram, and medical records use kilograms. The US and Canada use pounds for body weight in everyday speech, and the Netherlands uses kilograms throughout. This is why bathroom scales sold in the UK often switch between st, lb and kg.
Tip: if a health tool asks for your weight, check the units twice. Entering 12 (stone) into a box that expects kilograms gives a BMI less than a fifth of the real figure.
Convert it instantly
Use our stone to kilogram converter for any value, or the BMI calculator, which accepts stone and pounds directly.
Frequently asked questions
How many kg is 1 stone?
Exactly 6.35029318 kg, which is about 6.35 kg.
How many pounds are in a stone?
Exactly 14 pounds.
How do I convert 70 kg to stone?
Divide by 6.35029318 to get 11.02 stone. The decimal part, 0.02 × 14, is about 0.3 lb, so 70 kg is about 11 st 0 lb.
Sources
- NIST Special Publication 811, Appendix B: conversion factors (1 lb = 0.45359237 kg)
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