How to Use This Tool
Kilograms to pounds is a single multiplication and hardly needs a tool. Stones are the reason this page exists. British body weight is spoken as “eleven stone four” — a mixed-radix format with fourteen pounds to the stone — and almost every converter returns “11.29 stone” instead, which is technically correct and completely useless if you are trying to tell a nurse your weight.
The three boxes are all live
Type in any one and the other two follow immediately. The stone field is split in two so you can enter
11 and 4 the way you would say it. Underneath, the panel writes the weight out in
plain words, which is the form you actually need when reading it aloud or filling in a form that expects
stones and pounds separately.
The exact factors
One pound is exactly 0.45359237 kg, fixed by the 1959 international agreement. One stone is exactly fourteen pounds, so 6.35029318 kg. Both are definitions, not measurements, so the conversion introduces no error at all. The familiar shortcut of “multiply kilos by 2.2” is off by about 0.5%, which is roughly 350 g on a 70 kg adult — irrelevant for a bathroom scale, not irrelevant for a suitcase at an airline weight limit.
The mistake this prevents
“11.3 stone” and “11 stone 3” look almost identical and differ by more than a pound. The first is 11 st 4.2 lb; the second is 11.21 stone. People transcribing a weight from a decimal converter into a form that asks for stones and pounds make this substitution constantly, and nothing about the two numbers looks wrong.
The difference tracker
The box near the bottom compares your weight to a target and expresses the gap in all three units at once. This is the part people usually get wrong mentally, because a change of one kilogram is 2.2 pounds but only 0.157 stone, and small stone figures round to something that looks like no progress at all. Seeing the same change in pounds is often more encouraging and equally true.
What this tool will not do
It converts mass, not body composition, and it takes no view on what any number means for your health. Weight alone is a poor signal on its own; if that is what you are after, waist-to-height ratio is a better starting point than any single weight figure.
