Stones and Pounds to Kilograms Converter
Convert between stones+pounds (UK) and kilograms (metric) instantly. 1 stone = 6.35029 kg = 14 pounds. 1 pound = 0.453592 kg. Use this tool for body weight (NHS uses kg; weighing scales often show stones), baby weight, or any imperial-to-metric weight conversion.
Convert
How to Use This Stones to Kg Converter
- Enter stones and pounds in the left fields to see the kilograms equivalent on the right.
- Or enter kilograms directly into the right field — stones and pounds update automatically.
- Read additional units below: total pounds, grams, US tons, metric tonnes.
- Both directions update live as you type. No "Convert" button needed.
Conversion Formulas
Exact conversion factors:
- 1 stone = 14 pounds = 6.35029318 kg (international avoirdupois pound, defined by the International Yard and Pound Agreement of 1959).
- 1 pound = 0.45359237 kg exactly.
- To convert stones + pounds → kg: kg = (stones × 6.35029) + (pounds × 0.45359).
- To convert kg → stones + pounds: total pounds = kg ÷ 0.45359; stones = floor(total pounds ÷ 14); remaining pounds = total pounds − (stones × 14).
For everyday use, you can approximate: 1 stone ≈ 6.35 kg, or 1 kg ≈ 2.2 lb. The exact factor matters when reporting medical or scientific measurements.
Worked Example — UK Adult Weight
An adult weighs 13 stone 4 pounds at the gym. Convert to kg for the NHS form:
- 13 × 6.35029 = 82.554 kg
- 4 × 0.45359 = 1.814 kg
- Total = 84.37 kg
Worked Example — Baby Weight
A newborn weighs 7 lb 6 oz. To convert via stones-and-pounds form:
- 7 lb 6 oz = 7.375 pounds (6 oz = 6/16 lb = 0.375 lb)
- 0 stones × 6.35 + 7.375 × 0.45359 = 3.345 kg (about 3.35 kg or 3,345 g)
UK Weight Reference Chart
| Stones | Pounds | Kilograms | Total lb |
|---|---|---|---|
| 8 | 0 | 50.8 kg | 112 lb |
| 9 | 0 | 57.2 kg | 126 lb |
| 10 | 0 | 63.5 kg | 140 lb |
| 11 | 0 | 69.9 kg | 154 lb |
| 12 | 0 | 76.2 kg | 168 lb |
| 13 | 0 | 82.6 kg | 182 lb |
| 14 | 0 | 88.9 kg | 196 lb |
| 15 | 0 | 95.3 kg | 210 lb |
| 16 | 0 | 101.6 kg | 224 lb |
| 17 | 0 | 108.0 kg | 238 lb |
| 18 | 0 | 114.3 kg | 252 lb |
| 20 | 0 | 127.0 kg | 280 lb |
Common Scenarios
NHS appointments and prescriptions
The NHS uses kilograms for all clinical measurements (weight-based drug dosing, fluid calculations, BMI). Home scales in the UK often display stones-and-pounds. Convert before your appointment to give an accurate weight in kg.
BMI calculation
BMI uses metric: kg ÷ height(m)². Imperial BMI uses: 703 × lb ÷ height(in)². Most online BMI calculators (including ours) auto-convert if you enter stones+pounds. Try the BMI Calculator.
Weight loss target in kg
Losing 1 stone = 6.35 kg. Losing 2 stone = 12.7 kg. Losing 3 stone = 19.05 kg. Most health authorities recommend 0.5–1 kg/week sustainable rate. For target setting, see our Calorie Calculator.
Baby weight at birth
Average UK newborn: 7 lb 8 oz (3.4 kg). 5 lb (2.27 kg) is the low-birthweight threshold. Over 10 lb (4.54 kg) is macrosomia. Always confirm clinical values with your midwife — small kg differences can be clinically significant.
Luggage and shipping
Most UK airlines specify checked luggage in kg (typically 23 kg). US carriers often use 50 lb (22.68 kg). Use the converter to confirm your luggage will pass the limit either way.
Tips and Considerations
- UK home scales vary. Some display stones+pounds, some kg+grams, some pounds only. Check the unit before reading.
- US "tons" vs UK "tonnes". US ton = 2,000 lb = 907 kg. UK long ton = 2,240 lb = 1,016 kg. Metric tonne = 1,000 kg. Be careful with international shipping or scientific data.
- Ounces matter for babies. 1 lb = 16 oz, so 7 lb 8 oz ≠ 7.8 lb. Convert correctly: 7.5 lb, then × 0.4536 = 3.40 kg.
- Don't confuse "stone" with "pound". 14 lb = 1 stone. People sometimes say "I weigh 130" — if UK, this almost always means pounds (= 9 st 4 lb); if US, also pounds.
Related Calculators
- BMI Calculator — uses your weight in kg or stones+pounds.
- Healthy Weight Calculator — see your healthy weight range.
- Ideal Weight Calculator — Devine/Robinson/Hamwi formulas.
- Calorie Calculator — daily calorie needs by goal.
- Unit Converter — all unit conversions in one place.
Sources & References
- International Yard and Pound Agreement (1959) — definitive 0.45359237 kg/lb factor.
- BIPM — SI base units.
- NHS — kg is the clinical standard in UK healthcare.
Frequently Asked Questions
How many kg in a stone?
Exactly 6.35029318 kg. Often rounded to 6.35 kg for everyday calculations.
How many pounds in a stone?
Exactly 14 pounds. 1 stone = 14 lb.
How do I convert 11 stone 7 lb to kg?
11 × 6.35029 = 69.85 kg, plus 7 × 0.45359 = 3.18 kg. Total: 73.03 kg.
What is 70 kg in stones and pounds?
70 ÷ 6.35029 = 11.024 stones = 11 stone with 0.024 × 14 = 0.34 pounds remaining. So 70 kg = 11 stone 0.3 lb (approximately 11 st 0 lb).
Is "stone" used outside the UK?
Mostly UK and Ireland. The US uses pounds throughout (no stones). Australia and Canada use kg primarily but understand stones.
How accurate is "1 kg = 2.2 lb"?
It's an approximation. The exact factor is 1 kg = 2.20462 lb. Over 100 kg, the rounding error is 0.46 lb — not enough to matter for casual conversions but matters for clinical or shipping calculations.
Why does the UK still use stones?
Historical convention, plus stones are convenient for body weight (most people fall in 6–25 stones). The NHS uses kg formally but many UK adults instinctively think in stones for their own body weight.
How do I weigh in kg if my scale shows stones?
Most digital UK scales have a unit toggle (kg / st-lb / lb). Look for a button on the side or bottom. Or use this converter after reading the stones+pounds value.
Last reviewed: 18 May 2026. Conversion factors verified against International Yard and Pound Agreement (1959).