How this instrument works
One stone is fourteen avoirdupois pounds, where fourteen is an integer laid down by statute rather than some factor anyone measured. Before 1835 almost nothing about it was settled: butchers at Smithfield reckoned meat in stones of eight pounds, glaziers worked to five, cheesemongers to sixteen, wool merchants to fourteen or twenty-four depending on which port they shipped through. Britain's Weights and Measures Act of 1835 gave legal force to one stone of fourteen pounds, striking out every rival.
Fourteen looks arbitrary until you climb imperial mass upward. Sixteen ounces make one pound, fourteen pounds one stone, eight stone one hundredweight of 112 lb, twenty hundredweight one long ton of 2,240 lb. Every rung above the pound halves cleanly three times over — real convenience in market halls where sacks were split by hand rather than calculated. American practice broke off that ladder early: their hundredweight is 100 lb exactly, their short ton 2,000 lb, and no rung at all survives between pound and hundredweight.
Britain withdrew stone from its list of units legal for trade in 1985, yet it thrives wherever money is not changing hands. GPs across Britain and Ireland still note patients in stone plus pounds, racing cards publish jockey weights and handicaps in it, British boxing writers describe that sport's 154 lb ceiling as eleven stone without pausing. Americans, Canadians, Australians count body weight in plain pounds or kilograms, and tend to find such readings opaque on sight.
- Type your weight into the Stone (st) field; 11 is loaded there already.
- Enter whole stone as whole numbers; for fractions use decimals, where one quarter is 0.25 and half is 0.5.
- Read your answer from Pounds (lb). It recomputes on every keystroke.
- Reading 11 st 4 lb on your scale? Convert 11 first, then add 4 to what Pounds (lb) shows — never type 11.4.
Worked example — making eleven stone before weigh-in
One Manchester light-middleweight is told to make 11 st for his bout, sanctioned under American rules, where every document from his promoter quotes limits in pounds only. He types 11 into Stone (st), and Pounds (lb) returns 154.0 — precisely that division's ceiling. Nothing was lost in translation, because 11 × 14 is an integer times an integer.
His margin for error is where care pays. Weigh in at 11 st 3 lb instead and he stands at 157 lb, three pounds over, off the card. Typing 11.3 into Stone (st) would report 158.2 lb, something different again, since 0.3 of it is 4.2 lb rather than 3. Convert whole stone first, add loose pounds afterwards, and mixed readings never bite.
Questions
Is 14 pounds per stone exact, or rounded?
Exact, and more strictly so than most unit factors manage. Fourteen is counted, not measured: one stone holds fourteen pounds by law, so any whole count converts to whole pounds with nothing left to round. Contrast conversion into kilograms, which runs through 0.45359237 kg per pound, landing on 6.35029318 kg — equally exact, yet hardly something anyone carries in their head.
Why does 11.5 stone give 161 lb and not 11 st 5 lb?
Because decimals count fractions of stone, not loose pounds. Half of fourteen is seven, so 11.5 st means 11 st 7 lb, giving 11 × 14 + 7 = 161 lb. Written 11 st 5 lb, that figure would instead be 159 lb, or 11.357 st in decimal form. Confusing those two notations is far and away the commonest error with this unit: keep decimals for calculators, st-and-lb for scales.
Do British and American pounds weigh the same?
Identically. Both are international avoirdupois pounds of exactly 0.45359237 kg, agreed in 1959 by standards bodies across six English-speaking countries. What diverges is everything stacked above: imperial groups 14 lb into one stone, 112 lb into one hundredweight, while US customary skips that rung entirely, rounding its hundredweight to 100 lb. So 11 st is 154 lb on either side of the Atlantic — though only one side reads 11 st fluently.
Does anyone in America use stone?
Almost nobody. Scales, medical charts, gym equipment across North America all report body weight in whole pounds, so 154 lb stays exactly that, never becoming eleven stone. It endures in Britain and Ireland for people, surfacing internationally through horse racing plus boxing coverage, but US clinicians handed such figures reach for converters first.
How do I turn pounds back into stone and pounds?
Divide by 14, keeping whatever remains. 200 lb ÷ 14 leaves 14 remainder 4, so 200 lb reads as 14 st 4 lb. Prefer decimals and 200 ÷ 14 gives 14.286 st. Both describe one identical weight — remainder form is what British scales and clinic notes print, decimal form is what belongs in your Stone (st) field.
Why fourteen, rather than ten or sixteen?
Fourteen came out of medieval wool exporting, where one sack was reckoned at 26 stone and duty charged by weight; fourteen-pound stones squared those sums against hundredweights of 112 lb already in circulation. Rival stones lived on beside it for centuries — eight pounds for meat, five for glass, sixteen for cheese, all perfectly legal locally — until Britain's 1835 Act ended that muddle by promoting one of them, abolishing everything else. Its name is literal, too: early traders balanced goods against physical lumps of rock kept at each market, which is precisely why local values drifted so far apart.