Stone to kg: Convert Stones to Kilograms
Convert stone to kg with the exact factor: 1 stone equals 6.35 kg. Learn the formula, how UK body weight maps to metric, and common stone-to-kg values.
Why Stones to kg Comes Up
In the UK and Ireland, adult body weight is still spoken of in stones, but scales, gym equipment, and medical records increasingly show kilograms. Moving between the two is a daily need for anyone tracking weight across systems.
One stone equals 6.35029318 kg. Our stone to kg converter does the math both ways; the factor below is handy for quick estimates.
The Stone to kg Formula
One stone is defined as exactly 6.35029318 kilograms (14 pounds). To convert stones to kilograms, multiply the stone value by 6.35029318.
The Exact Calculation
For 1 stone: 1 × 6.35029318 = 6.35029318 kg, rounded to 6.35 kg. For 10 stone: 10 × 6.35029318 = 63.5029 kg, about 63.5 kg.
The multiplication works for any weight, including the "stones and pounds" format. For 11 st 2 lb, convert the 11 stone (69.85 kg) and add 2 lb (0.907 kg) for 70.76 kg.
Why Multiply by 6.35
The stone was fixed at 14 pounds, and the pound is 0.45359237 kg, so 14 × 0.45359237 = 6.35029318 kg per stone. Multiplying stones by that figure answers "how many kilograms make up this mass."
What the Numbers Look Like
Common body weights: 10 stone = 63.5 kg, 12 stone = 76.2 kg, 14 stone = 88.9 kg. UK charts often split the remainder into pounds, so 12 st 5 lb means 12 stone plus 5 pounds, or about 78.2 kg.
If you only know your weight in stones, multiplying by 6.35 gives the kilogram figure most apps and scales expect. The reverse is in our kg to stone guide.
Stone to kg Compared With Nearby Values
Reference points: 8 stone = 50.8 kg, 9 stone = 57.2 kg, 11 stone = 69.9 kg. Each stone adds a steady 6.35 kg, so the metric number climbs predictably.
For typical adult weights, the stone figure of 8-16 st maps to about 51-102 kg on metric scales.
When You Need Stones in kg
The conversion matters for health tracking. A UK weight of 13 stone is 82.55 kg, the number a metric fitness app wants. Diet plans, BMI calculators, and pharmacy scales usually expect kilograms.
It also helps when reading international health advice that quotes metric weights while your own records use stones.
Frequently Asked Questions
How many kg is 1 stone?
1 stone equals exactly 6.35029318 kg, about 6.35 kg.
How do I convert stone to kg?
Multiply the stone value by 6.35029318. For 12 stone: 12 × 6.3503 = 76.2 kg.
How many kg is 10 stone?
10 stone equals 63.5029 kg, normally rounded to 63.5 kg.
Why is a stone 14 pounds?
The stone was traditionally standardized as 14 pounds; with the pound defined as 0.45359237 kg, that gives 6.35029318 kg.
What is 11 st 2 lb in kg?
11 stone is 69.85 kg and 2 lb is 0.907 kg, so 11 st 2 lb is about 70.76 kg.
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Quick Summary
1 stone equals 6.3503 kg. Multiply stones by 6.35029318 (the exact kg per stone): 1 × 6.3503 = 6.35 kg. Ten stone is exactly 63.5 kg.
Related Guide
kg to Stone: Convert Kilograms to Stones
Convert kg to stone with the exact factor: 1 kg equals 0.1575 stone. Learn the formula, why the UK uses stones for body weight, and how to switch between the systems.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 pound (lb, avoirdupois) = 0.45359237 kilograms (exact)
- EXACT1 ounce (oz, avoirdupois) = 28.349523125 grams (exact, 1/16 lb)
- EXACT1 stone (st) = 6.35029318 kilograms (exact, 14 lb)
- EXACT1 short ton (US) = 907.18474 kilograms (exact, 2000 lb)
Common Pitfalls & How to Avoid Them
Mass vs. weight
The pound and kilogram are units of MASS, not force. On Earth, mass and "weight" read the same number in practice, but a 70 kg mass weighs less on the Moon. UnitFig converts mass; for scientific force you need newtons (1 lbf = 4.4482216152605 N, exact).
Avoirdupois vs. troy ounce
Cooking and body weight use the avoirdupois ounce (28.349523125 g). Gold and precious metals use the troy ounce (31.1034768 g). Never mix them — the error is about 10%.
Rounding the factor
Using 2.2 instead of the exact 2.20462262 overstates small errors at large values. For medical dosing or competition weight classes, keep the full factor or use a converter.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
Last Updated 2026 | This article was reviewed for accuracy