Stone is the go-to weight unit for body weight in the United Kingdom and Ireland, but if you're from virtually anywhere else in the world, you think in kilograms. This converter bridges that gap, letting you instantly translate stone measurements into the metric kilograms used by doctors, scientists, and most of the global population. Whether you're filling out an international medical form, comparing fitness progress with friends abroad, or just curious what "12 stone" actually means, this guide covers everything you need.
One stone is defined as exactly 14 pounds, which converts to 6.35029318 kilograms. The stone has been a unit of weight in England since before the Norman Conquest and was formally standardized in 1985. Despite the UK's metrication, it remains the most common way British people describe their own body weight.
| Stone (st) | Kilograms (kg) | Pounds (lbs) |
|---|---|---|
| 6 stone | 38.10 kg | 84 lbs |
| 7 stone | 44.45 kg | 98 lbs |
| 8 stone | 50.80 kg | 112 lbs |
| 9 stone | 57.15 kg | 126 lbs |
| 10 stone | 63.50 kg | 140 lbs |
| 11 stone | 69.85 kg | 154 lbs |
| 12 stone | 76.20 kg | 168 lbs |
| 13 stone | 82.55 kg | 182 lbs |
| 14 stone | 88.90 kg | 196 lbs |
| 15 stone | 95.25 kg | 210 lbs |
| 16 stone | 101.60 kg | 224 lbs |
| 18 stone | 114.31 kg | 252 lbs |
| 20 stone | 127.01 kg | 280 lbs |
International medical forms typically ask for weight in kilograms. If you know your weight as "11 stone 7," you'd convert: 11 × 6.35 + (7 × 0.4536) = 69.85 + 3.18 = 73.03 kg. Many UK doctors record weight in kg internally but communicate in stone with patients, creating a frequent need for this conversion.
Fitness apps like MyFitnessPal and Strava use kilograms by default. If you set a goal to lose "1 stone," that's 6.35 kg — a substantial and measurable milestone. Tracking progress in kg also makes it easier to compare with global fitness communities online.
British newspapers, TV shows, and sports commentators routinely use stone. "The boxer weighed in at 14 stone 4" means 90.72 kg. A celebrity "dropping to 9 stone" means reaching 57.15 kg. Without this conversion, these references can be confusing for international audiences.
Some travel insurance policies and airline baggage allowances reference stone in UK-specific documentation. Converting to kg ensures you understand the limits when booking with international carriers.
Multiply stone by 6.35 for a quick estimate. For easier mental math: multiply by 6, then add half the original number plus a tiny bit more. For 11 stone: 11 × 6 = 66, then 11 × 0.35 ≈ 3.85, total ≈ 69.85 kg. This approximation is accurate enough for most purposes.
The metric system was adopted by most countries during the 19th and 20th centuries as part of international standardization. The UK began metrication in 1965 but kept stone for body weight due to strong public preference. The US, meanwhile, uses pounds rather than stone for body weight.
We use the exact international definition of 6.35029318 kg per stone, providing precision to multiple decimal places. For practical purposes, 6.35 is sufficient and matches the accuracy of most digital scales.
Historically, stone was used for wool, meat, and other commodities (with varying weights per goods type). Today, its use is almost exclusively for human body weight in the UK and Ireland.
For an average-height adult (170 cm / 5'7"), a healthy BMI (18.5–24.9) corresponds to roughly 9.5 to 12.8 stone (60.5 to 81.6 kg). However, ideal weight depends on many factors including height, age, and body composition.
Use our free online Stone to KG converter for instant, accurate conversions every time.