The unit definitions
- 1 stone
- 14 pounds
- 1 pound
- 0.45359237 kilograms
- 1 stone
- 6.35029318 kilograms
- 1 pound
- 16 ounces
The pound-to-kilogram value follows the international avoirdupois pound definition. It is listed in the NIST Guide to the SI conversion factors.
Stone and pounds to kilograms
First convert the complete measurement into pounds, then multiply by the exact kilogram value of one pound.
kg = (stone × 14 + pounds) × 0.45359237
Worked example: 11 st 7 lb
(11 × 14 + 7) × 0.45359237
= 161 × 0.45359237
= 73.02837157 kg
= 73.03 kg when displayed
Kilograms to stone and pounds
Divide kilograms by 0.45359237 to find total pounds. Each complete group of 14 pounds forms one stone; the remainder is displayed as pounds.
total lb = kg ÷ 0.45359237
The primary result uses one decimal place for the remaining pounds. A second result converts the fractional pound into ounces, and a third shows the complete measurement as decimal stones.
Decimal stones
A decimal after the stone value represents a fraction of a whole stone. It is not a pounds value. For example, 0.5 stone is half of 14 pounds, which is 7 pounds.
11.5 st = 11 st 7 lb
11.3 st = 11 st 4.2 lb, not 11 st 3 lb.
Rounding
- Kilogram answers are displayed to two decimal places.
- Remaining pounds are displayed to one decimal place.
- Pounds-and-ounces results use the nearest whole ounce, carrying 16 ounces into one pound and 14 pounds into one stone.
- Decimal-stone results are displayed to two decimal places.
- All intermediate calculations retain full precision.