Stones to Kilograms conversion

Stones to kilograms

Most of the world weighs people in kilograms, so a weight given in stones — the traditional British unit — often has to be converted before it can be entered into a form, a fitness app or a medical record. One stone is defined as 14 pounds, and since a pound is exactly 0.45359237 kg, one stone is 6.35029 kilograms.

Doing the conversion

Multiply the number of stones by 6.35029. If the weight is given as stones and pounds, convert the pounds separately (multiply by 0.4536) and add the two results. Example: 10 st 6 lb = 10 × 6.35029 + 6 × 0.4536 = 63.50 + 2.72 = 66.2 kg.

A quick approximation is to multiply by 6.35, or to remember that 1 stone is about 6 and a third kilograms.

Typical values

• 8 st = 50.8 kg
• 9 st = 57.15 kg
• 10 st = 63.5 kg
• 11 st = 69.85 kg
• 12 st = 76.2 kg
• 13 st = 82.55 kg
• 14 st = 88.9 kg
• 15 st = 95.25 kg

Why the stone is 14 pounds

Historically stones varied by region and by the goods being weighed — a stone of wool was different from a stone of cheese. An Act of Parliament in 1835 fixed the stone at 14 pounds for general use, and that is the value that survived. It is a convenient size for body weight: a typical adult falls between 8 and 16 stones, so the numbers stay small and easy to say.

When precision matters

For medication dosing, sports weight classes and BMI calculations use the full factor 6.35029 and include the pounds part of the weight. A rounded "6.35" is fine for conversation but can shift a BMI figure by a tenth of a point.