What this calculator does
Turn a weight in stone into kilograms, or kilograms into stone, in one quick step. The stone is an old British (imperial) unit of 14 pounds. Today it survives mainly for body weight in the United Kingdom and Ireland. Bathroom scales, slimming clubs and casual conversation there use stones and pounds. Doctors, gyms and almost every other country use kilograms.
Because the pound is exactly 0.45359237 kg, a stone of 14 pounds is exactly 6.35029318 kg. Stones to kilograms multiplies by that figure, and kilograms to stones divides by it. Pick a direction and the working shows the factor.
Where it's used
Why this math matters outside the classroom:
- Body weight. Someone weighing 11 stone weighs about 69.9 kg.
- Sports weigh-ins. UK horse racing often gives weights in stone, and a 63.5 kg rider is about 10 stone.
- Bathroom scales. A reading of 12 st 7 lb is 12.5 stone, or about 79.4 kg.
- Exact definition. Students derive the factor from 14 lb × 0.45359237 kg = 6.35029318 kg.
- Weight changes. Fitness apps convert a 2 stone change in weight into about 12.7 kg.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the weight as a decimal number of stones or kilograms, such as 11 st or 72.5 kg.
- If your weight is in stones and pounds, turn the pounds into a fraction of a stone first: 10 st 7 lb is 10 + 7/14 = 10.5 st.
- Choose the direction and read the result and the reference table.
What the inputs mean
- Value to convert
- A weight in decimal stones (for st → kg) or kilograms (for kg → st).
- Direction
- Choose stones to kilograms or the reverse.
Formula and method
kg = st × 6.35029318 st = kg ÷ 6.35029318 ≈ kg × 0.157473044
In the formulas, st is the weight in stones and kg is the weight in kilograms.
1 st = 14 lb (pounds) and 1 lb = 0.45359237 kg, both exact. So 1 st = 14 × 0.45359237 = 6.35029318 kg.
Going the other way, about 0.1574730 stone per kilogram, the decimals go on forever. The calculator divides by the exact 6.35029318 instead.
Worked example
Convert a weight of 11 stone to kilograms.
- 1 st = 6.35029318 kg exactly.
- 11 × 6.35029318 = 69.85322498.
Result: 11 st is about 69.85 kg.
Understanding the result
Mental shortcut: a stone is a little over 6⅓ kg. Multiplying by 6.4 overstates by under 1%, so 10 st becomes 64 kg against an exact 63.50 kg. For kilograms to stone, divide by 6.35, or multiply by 0.16 for a figure about 1.6% too high.
Reference points: 10 st ≈ 63.50 kg; 12 st ≈ 76.20 kg; 70 kg ≈ 11.02 st; 80 kg ≈ 12.60 st.
Watch the decimals. 12.6 st is not 12 st 6 lb. The .6 is six tenths of a stone, which is 0.6 × 14 = 8.4 lb, so 12.6 st is about 12 st 8 lb. Use the stone-to-pounds page if you need the remainder in pounds.
Assumptions and limitations
- The stone is the imperial stone of exactly 14 international pounds.
- Stones-and-pounds readings must be entered as decimal stones.
- The result is in decimal stones; it is not split into stones and pounds.
Frequently asked questions
How many kilograms are in a stone?
Exactly 6.35029318 kg, which most people round to 6.35 kg.
How do I enter 11 st 4 lb?
Divide the pounds by 14 and add them: 11 + 4/14 ≈ 11.2857 st. That is about 71.67 kg.
Is the stone used outside the UK and Ireland?
It is rarely used elsewhere. The plural is often left as "stone" ("she weighs nine stone"), and the abbreviation is st.
How this calculator is checked
Method: 1 st = 14 lb; 1 lb = 0.45359237 kg exactly; hence 1 st = 6.35029318 kg. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
Embed this calculator
Put this Stone to Kilograms Converter on your own website or blog for free. Paste this code where you want it to appear: