Stone and kilograms
The stone is exactly 14 pounds, or 6.35029318 kilograms. People in the UK and Ireland often state body weight in stone and pounds, for example 11 st 4 lb.
The kilogram is the SI base unit of mass, defined since 2019 by fixing the Planck constant. Body weight, groceries, luggage allowances and most product weights outside the US are given in kilograms.
Worked example
Convert 12 st: 12 × 6.35029318 = 76.20351816, so 12 stone is 76.20351816 kilograms. Likewise 20 st = 127.0058636 kg.
Estimating in your head
Multiply by 6.4 for a quick figure; it is off by about 0.8%. For 12 st that gives 76.8 kg, against 76.2035 exactly.
Going the other way
To convert kilograms to stone, divide by 6.35029318 (or multiply by 0.157473044418). The swap button between the boxes opens that page.
How this works
kg = st × 6.35029318
1 st = 6.35029318 kg and 1 kg = 1 kg, both by definition, so the factor is their ratio: 6.35029318 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many kilograms are in a stone?
1 stone = 6.35029318 kilograms, exactly. The value follows from the unit definitions, so it never changes.
How do I convert stone to kilograms?
Multiply by 6.35029318. For example, 20 st × 6.35029318 = 127.0058636 kg.
What is 100 st in kilograms?
100 st = 635.029318 kg. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- Federal Register 59-5442 (1959) — Refinement of values for the yard and the pound
- Wikipedia — Avoirdupois system
Reviewed Oct 17, 2026 · test vectors fixtures/units/mass/stone-to-kg/