Convert Stones to Kilograms
Convert stones into kilograms when entering body weight on a non-UK medical form, fitness tracker or international shipping declaration.
1 st = 6.3503 kg
One stone equals exactly 6.35029318 kilograms. To convert stone to kilograms, multiply by 6.35029318 — so 11 st = 69.85 kg and 14 st = 88.90 kg. Since a stone is defined as 14 avoirdupois pounds and the pound is exactly 0.45359237 kg, this conversion is exact rather than approximate. A quick approximation is to multiply by six and add five percent, which puts 12 st at 72 plus 3.6, or about 76 kg against the true 76.2. The arithmetic error to avoid is treating the fractional part as tenths: 12.5 st is 12 st 7 lb, or 79.4 kg, not 12 st 5 lb. Because the stone was standardised for wool and other goods at differing weights before 1835, historical references to stones are unreliable without knowing which trade they came from. Medical records in the UK now use kilograms, so a weight quoted in stone is almost always self-reported.
Quick reference: stones to kilograms
| Stones | Kilograms |
|---|---|
| 7 | 44.45 kg |
| 8 | 50.80 kg |
| 9 | 57.15 kg |
| 10 | 63.50 kg |
| 11 | 69.85 kg |
| 12 | 76.20 kg |
| 13 | 82.55 kg |
| 15 | 95.25 kg |
| 20 | 127.01 kg |
How do you convert stones to kilograms?
Formula: kilograms = stone × 6.35029318 • 11 stone → 11 × 6.35029318 = 69.85 kg. • 12 stone 6 pounds → convert the pounds first: 6 ÷ 14 = 0.4286 stone, so 12.4286 × 6.35029318 = 78.93 kg. • 15 stone → 15 × 6.35029318 = 95.25 kg, a figure that appears frequently in BMI charts published for UK audiences.
When and why people use stones to kilograms
Filling in medical and official forms is the main driver. UK and Irish patients know their weight in stones and pounds while every clinical system records kilograms, so the conversion happens constantly in GP surgeries, hospitals and insurance paperwork. BMI calculation is a specific instance worth separating out. The BMI formula requires kilograms and metres, so a weight in stones and a height in feet and inches both need converting before the index can be computed — and doing the conversion badly is a common source of wrong BMI figures. Equipment ratings are the third case. Weight limits on ladders, hammocks, exercise machines and passenger lifts are published in kilograms under EU and UK standards, so anyone checking whether they are within a limit has to convert from the units they normally use.
Common mistakes to watch for when converting stones to kilograms
The most frequent mistake is handling the pounds component wrongly. A weight of 12 stone 6 is not 12.6 stone — the 6 pounds must be divided by 14 to give 0.4286 stone. Treating it as a decimal overstates the weight by about 1.1 kg. A second error is using 6.35 rather than the full 6.35029318 for anything precise; the difference is small but real across large weights. Third, some older references use a stone of 8, 12 or 16 pounds for particular commodities such as wool or meat, a historical quirk that survives in archival documents and will produce nonsense if applied to body weight. Finally, when converting for BMI, remember height must be in metres and squared — mixing a metric weight with an imperial height is the classic BMI error.
How to estimate stones to kilograms in your head
Multiply by 6 and add about 6%. For 12 stone: 12 × 6 = 72, plus 4.3 gives 76.3 kg against a true 76.2. The alternative two-step route is to convert to pounds first by multiplying by 14, then halve and subtract a tenth. For 12 stone: 12 × 14 = 168 lb, half is 84, minus 8.4 gives 75.6 kg — slightly low but quick. Anchors: 8 st ≈ 51 kg, 10 st ≈ 63.5 kg, 12 st ≈ 76 kg, 14 st ≈ 89 kg, 16 st ≈ 102 kg. When a weight includes pounds, convert those separately at roughly 0.45 kg each rather than trying to fold them into the stone figure — 12 st 6 lb is 76.2 plus 2.7, or 78.9 kg.
Stones to Kilograms FAQ
How many kg is 11 stone?
- 69.85 kg.
How do I convert 12 stone 6 pounds?
- Divide the pounds by 14 first: 6 ÷ 14 = 0.4286. Then (12 + 0.4286) × 6.35029318 = 78.93 kg.
Is 12 stone 6 the same as 12.6 stone?
- No. 12.6 stone is 12 stone 8.4 pounds. The pounds component must be divided by 14, not treated as a decimal.
How many pounds is a stone?
- 14 pounds exactly, which is 6.35029318 kg.
What weight in kg is 14 stone?
- 88.90 kg.
Do I need kilograms for BMI?
- Yes. BMI is weight in kilograms divided by height in metres squared, so both values must be metric before the formula is applied.
Were there other kinds of stone?
- Historically yes — stones of 8, 12 and 16 pounds existed for specific goods such as wool. Only the 14-pound stone applies to body weight.
How do I convert stone directly to pounds?
- Multiply by 14. So 11 stone is 154 lb, and 11 stone 4 is 158 lb. Pounds are the unit to use when sharing a weight with a US audience.
Why does the UK still use stones for body weight?
- It persists in speech and on domestic scales even though it was removed from legal trade use. Medical records are metric, so patients and clinicians routinely convert during consultations.
Is my input logged?
- No. The conversion runs in your browser and nothing is transmitted.
Last updated:
Sources: 1959 international yard and pound agreement; UK Weights and Measures Act 1985; WHO BMI classification guidance requiring kg and m² inputs.