Read a mixed stone and pound weight
A weight written as “11 st 3 lb” contains two parts of the same mass measurement. One stone equals exactly 14 avoirdupois pounds. Convert the stone component to pounds, add the remaining pounds, and then apply the exact international pound-to-kilogram factor of 0.45359237. The two input boxes avoid treating the entire expression as a decimal number: 11 stone 3 pounds is not 11.3 stone. This distinction matters when copying a health record, sports weigh-in, or older British measurement into a system that expects kilograms. Enter the remaining pounds from zero up to, but below, fourteen.
Work through 11 st 3 lb
For 11 stone 3 pounds, the stone portion is 11 × 14 = 154 pounds. Add 3 pounds to get a total of 157 pounds. Multiplying 157 by 0.45359237 gives 71.21400209 kilograms, or approximately 71.21 kg when two decimal places are suitable. The calculator shows both the intermediate total in pounds and the kilogram result so the arithmetic can be checked. If the pounds box shows 0, each whole stone contributes 6.35029318 kg. If a record contains 14 remaining pounds, carry that into one additional stone rather than entering an unnormalized pair.
Use and precision
This mixed-unit converter is useful when comparing body weight records from countries that use different units or entering a measurement into a medical, fitness, or shipping form. The mathematical factor is exact, but the original reading may be rounded. A bathroom scale reporting to the nearest pound does not justify reporting a kilogram figure to eight decimal places. Choose display precision that matches the input quality and the purpose. When two records differ by a small amount, first check whether they were measured under similar conditions and with comparable instruments, rather than attributing every difference to the unit conversion.
Avoid unit and notation mistakes
A pound in this context is a unit of mass, not a pound of force; pounds-force would require a different physical interpretation. A stone is not an SI unit, but the defined relation to the international pound makes the calculation straightforward. Do not mistake a slash or decimal separator in a handwritten entry for the division sign. Negative stones and negative remaining pounds are invalid for an ordinary nonnegative mass measurement. This calculator intentionally keeps the pound remainder below fourteen so a single mixed weight has one normalized expression. For a pounds-only value, put zero in the stone field and enter the pounds remainder if it is below fourteen; larger values should be split into stones and pounds.