Stone to Kg Converter

A stone is a British unit of weight equal to 14 pounds¹. A kilogram is the metric unit used by the NHS, airlines and most apps. To convert, turn stone and pounds into total pounds, then multiply by the exact kilogram value of one pound.

For the history of the stone and where it is still used, see our Stone to Lbs Converter and Lbs to Stone Converter.

What Stone to Kg Conversion Measures

This tool changes the unit, not the weight. 11 st 7 lb and 73.0 kg are the same weight written two ways. It does not weigh you, judge your weight or work out a medicine dose.

The Formula

UK weights and measures law defines the stone as 14 pounds and the pound as 0.453 592 37 kilogram¹. NIST lists the same stone and gives the pound as 453.592 37 grams, exactly².

Total pounds = (stone x 14) + pounds

Kilograms = total pounds x 0.45359237

One stone = 14 x 0.45359237 = 6.35029318 kg

Both numbers are defined, so the result is exact.

How This Calculator Computes Your Result

Type the whole stone in the Stone box and extra pounds in the Pounds box (half pounds are fine). The Stone box also takes decimal stone, so 10.5 means ten and a half stone. Pounds of 14 or more roll into stone, so 0 st 20 lb becomes 1 st 6 lb.

The tool rounds once, at the end. The main result shows kilograms to 1 decimal, in line with the 0.1 to 0.2 kg steps of a typical clinical scale³. A second line shows 2 decimals and your total pounds. Both are rounded from the exact value. The tool accepts 1 lb to 100 st, and the swap button converts kilograms back to stone.

What Your Result Means

Your result is your weight in kilograms. Use this table to check it. The last column adds half a stone (7 lb).

Each extra pound adds about 0.45 kg, so 5 lb is 2.27 kg and 10 lb is 4.54 kg. As a sanity check, the kilograms should be a little over 6 times the stone. If not, a unit was mixed up.

Why Clinics and Hospitals Record Weight in Kilograms

NHS England's data dictionary defines a person's weight in kilograms⁴. Weight is used for diagnosis, monitoring and treatment, including working out medicine doses, and an NHS Scotland safety notice warns that weighing errors can lead to under- or over-dosing³. In 2010, a Department of Health alert said scales bought for medical use in England should only show metric units, and that any imperial switch must be disabled⁵. The NHS also works out BMI from weight in kilograms and height in meters, and its own example is 70 kg, "around 11 stone"⁶.

So a GP system or hospital form will want 11 st 7 lb as 73.0 kg. When you give your weight by phone or on a form, state the unit. This tool only converts units. Doses are set by a prescriber or pharmacist.

Bags, Gyms and Apps That Use Kilograms

Airline limits are set in kilograms. easyJet, for example, sells 15 kg and 23 kg hold bags and caps any single bag at 32 kg⁷. A 23 kg limit is 3 st 8.7 lb. A common trick is to weigh yourself, then weigh yourself holding the case, and take the difference. At 11 st 2 lb alone and 14 st 10 lb with the case, the bag is 3 st 8 lb, or 22.7 kg. At 14 st 11 lb, it is 3 st 9 lb, or 23.1 kg, just over.

Gym machines, weight loss apps and smart scales often ask for a weight or goal in kilograms. Convert it here, then copy the figure across.

Reading 10.5 Stone as 10 Stone 5 Pounds

It is easy to write 10 st 5 lb as "10.5". But the part after a decimal point is a fraction of a stone, and a stone is 14 pounds¹. So 10.5 st is ten and a half stone, which is 10 st 7 lb, or 66.7 kg. The weight you meant, 10 st 5 lb, is 65.8 kg.

If you type a decimal such as 10.5 in the Stone box and leave Pounds empty, the tool offers a "Did you mean 10 st 5 lb?" button that fixes the entry.