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.

Worked examples

9 st 8 lb. 9 × 6.35029 = 57.15 kg, plus 8 × 0.4536 = 3.63 kg, total 60.8 kg.

12.5 st. As a decimal, 12.5 × 6.35029 = 79.4 kg. Note that 12.5 st is 12 st 7 lb, not 12 st 5 lb.

A 16-stone rugby forward. 16 × 6.35029 = 101.6 kg — the same figure you will see on a metric team sheet.

Frequently asked questions

How many kilograms is 1 stone? 6.35 kg. A quick approximation is "six and a third kilos".

How do I enter stones in a metric form? Convert stones and pounds separately and add them: stones × 6.35029 plus pounds × 0.45359.

Is a stone the same in Ireland and the UK? Yes — 14 pounds in both. Historically other countries had stones of 8 to 16 pounds, but those are long gone.

Related conversions

Stones to pounds is simply × 14; pounds to kilograms is × 0.4536. For the reverse, use the kilograms to stones converter.

Good to know

Weight classes in boxing and mixed martial arts show all three units side by side. Lightweight in boxing is 135 lb, which is 9 st 9 lb or 61.2 kg; heavyweight starts above 200 lb, 14 st 4 lb, 90.7 kg. British fight promoters announce weights in stones and pounds, American ones in pounds, international federations in kilograms, so the same fighter is "11 st 6 lb", "160 lb" and "72.6 kg" on the same evening. Horse racing in Britain and Ireland sets handicap weights in stones and pounds too — a jockey carrying "9 st 7 lb" is carrying 60.3 kg including saddle.