Stone to kilograms:
multiply by 6.35029

How many kilograms are in a stone?

One stone is 6.35029318 kilograms, or about 6.35 kg. A stone is 14 pounds, and one pound is exactly 0.45359237 kg, which gives the factor.

Stone is still the everyday unit for body weight in the UK and Ireland, so people there give their weight as, for example, 11 stone 4 pounds, while the rest of the world uses kilograms.

The stone is a traditional British unit of weight, fixed at 14 avoirdupois pounds. It survives mainly for human body weight in the UK and Ireland, so you will hear that someone is 12 stone or has lost half a stone, even though official and medical records are in kilograms. Because the pound is defined as exactly 0.45359237 kg, the stone is also exact: 14 × 0.45359237 gives 6.35029318 kg. That is why a converter can give the same answer every time, with no uncertainty in the factor itself.

The stone to kg formula

A whole-stone value is simpler. A person weighing 12 stone is 12 × 6.35029318 = 76.2035 kg. In the other direction, 75 kg is 75 ÷ 6.35029318 = 11.81 stone, which is 11 stone and about 11.3 pounds.

1. 1Write the weight in stone. Convert the extra pounds to a fraction of a stone by dividing by 14.
2. 2Multiply by 6.35029318.
3. 3Round to one decimal for body weight.
4. 4Check that the kg figure is about 6.35 times the stone figure.

Chart: stone to kilograms

Where stone to kg is needed

• Booking a flight or a medical form abroad that asks for weight in kilograms.
• Following a diet plan or a fitness app set up in kilograms when your scales show stone.
• Comparing a British health or sports page with a metric source, for example a boxing weight class.
• Reading older British documents that give weight in stone.

Quick sanity checks for stone to kilograms

Work in pounds as a cross-check. A weight of 8 stone 7 pounds is 119 pounds, and 119 × 0.45359237 = 53.98 kg. The stone method gives the same answer.

To go from kilograms to stone fast, multiply by 0.1574730444. A 90 kg person is 14.17 stone.

Each pound is about 0.45 kg, and each stone is 14 of them, so stone values stay close to one sixth of the kilogram figure.

Common mistakes when converting stone to kg

• Reading 11 stone 4 as 11.4 stone. The pounds are out of 14, so 4 pounds is 0.29 stone, and the weight is 11.29 stone.
• Confusing stone with pounds. A stone is 14 pounds, so multiplying stone by 0.4536 gives wrong answers.
• Using 6.3 or 6.5 loosely. 6.5 overstates a 12 stone person by about 1.8 kg.
• Rounding too early. Using 6 instead of 6.35 on a 15 stone weight leaves you more than 5 kg short.

Weight figures here are plain unit conversions, not health advice.