Fourteen pounds to the stone
The stone is fourteen avoirdupois pounds, which makes it exactly 6.35029318 kilograms. The awkward number fourteen is a historical accident: the stone was standardised at fourteen pounds for wool in 1389, and different trades used stones of eight, twelve or twenty-four pounds well into the nineteenth century.
Never write it as decimal stone
The most common error is treating “11 stone 4” as 11.4 stone. It is not — it is 11 + 4/14 = 11.286 stone, because the pounds are fourteenths, not tenths. Written as a decimal it comes to 158 lb, whereas 11.4 stone would be 159.6 lb. The page shows both forms so the difference is visible.
Where stone is still used
Britain and Ireland use stone almost exclusively for human body weight and essentially nowhere else — not for luggage, not for food, not for freight. Australia and New Zealand dropped it with metrication in the 1970s, and the United States never adopted it for personal weight, which is why Americans quote body weight in plain pounds. Medical records in the UK are metric, so patients routinely need this conversion in both directions.