Stones, Pounds, and Kilograms: How to Convert UK Body Weight
October 21, 2026
In the UK and Ireland, body weight is still commonly given in stones and pounds. One stone equals 14 pounds, or about 6.35 kilograms. To convert 12 stone 5 pounds to kilograms, first convert to pounds (12 × 14 + 5 = 173 lb), then multiply by 0.45359237 to get about 78.5 kg.
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The exact definition is 1 pound = 0.45359237 kg, which makes 1 stone = 14 × 0.45359237 = 6.35029 kg. Going the other way, 1 kg = 2.20462 lb = 0.157473 stone.
To go from kilograms to stones and pounds, divide by 6.35029, keep the whole stones, and convert the remainder to pounds: 80 kg is 12.6 stone, which is 12 stone and 0.6 × 14 ≈ 8.4 pounds, or 12 st 8 lb.
| Stones and pounds | Total pounds | Kilograms |
|---|---|---|
| 8 st 0 lb | 112 | 50.8 |
| 10 st 0 lb | 140 | 63.5 |
| 12 st 5 lb | 173 | 78.5 |
| 14 st 0 lb | 196 | 88.9 |
| 16 st 7 lb | 231 | 104.8 |
Worked Example
Convert 12 st 5 lb to kg. Pounds: 12 × 14 = 168, plus 5 = 173 lb. Kilograms: 173 × 0.45359237 = 78.47 kg. For the reverse, 70 kg × 2.20462 = 154.3 lb, which is 11 stone (154 lb) and 0.3 lb: roughly 11 st 0 lb.
The same pound conversion applies in the US, where weight is typically given in pounds only, so 173 lb is how an American would state the first example.
Why the Stone Persists
The stone was a historic unit of mass used in trade. UK law replaced it for trade use, but it stayed in everyday talk about people's weight, in NHS leaflets, and on bathroom scales. As a result, many British adults know their weight in stones but their height in feet and inches, while medical records use kilograms and metres.
When using BMI calculators or dosage charts, convert to kilograms first, because the standard formulas assume metric units.
Frequently Asked Questions
How many pounds are in a stone?
14 pounds.
How many kilograms are in a stone?
About 6.35 kg (6.35029 kg exactly).
How do I convert kg to stones and pounds?
Divide by 6.35029 to get stones, then multiply the decimal part by 14 for the remaining pounds.
Is the stone used outside the UK?
Rarely. It is used mainly in the UK and Ireland for body weight.