Stone to Kilograms Converter

The UK's 1995 metrication rules made kilograms and grams mandatory for retail trade — selling food, fuel, and most packaged goods by weight — but personal body weight was deliberately left outside that legal requirement. Bathroom scales, gym conversations, and casual NHS chat still default to stone and pounds by custom rather than law, which is why "I weigh 11 stone 4" remains completely normal in Britain and Ireland while a supermarket scale reads only in grams.

Yes — stone is almost always spoken and written as a whole number, or a whole number plus pounds (11 stone, or 11 st 6 lb), since 14 lb per stone is coarse enough that fractions of a stone rarely come up in conversation. Kilograms, by contrast, are typically reported to one decimal place (76.2 kg) because a kilogram is a much finer unit. Expect the kg side of any conversion to carry more visible precision than the stone side ever would.

Stone sits between the pound and the hundredweight in the old avoirdupois hierarchy: 14 lb make 1 stone, 2 stone make 1 quarter (28 lb), and 8 stone make 1 hundredweight (112 lb). Of that whole chain, only the pound and the stone survive in ordinary UK/Irish speech today — quarters and hundredweights are now mostly confined to historical records, agricultural contexts, and shipping paperwork.

Yes — this tool and its reverse (kg to stone) share one fixed constant, 6.35029318 kg per stone, just applied in opposite directions: multiply stone by that number to get kg, or divide kg by it to get stone. There's no separate "reverse" rounding rule, so converting a value to kg and back to stone always returns your original number, within normal decimal rounding.

For everyday purposes — checking your own body weight, a luggage limit, or a rough estimate — no, the difference is trivial: at 10 stone, the full factor gives 63.502932 kg while the truncated 6.35 gives 63.5 kg, a gap of under 3 grams. But the error scales with the value, so at 20 stone it grows to about 5.9 grams, and if a downstream calculation multiplies that kilogram figure by something else — a medication dose calculated in mg per kg of body weight, for instance — even a few grams of body-mass error can shift the computed dose measurably. The safest habit is to carry at least four decimal places (6.3503) through any calculation and round only the final answer, rather than rounding the conversion factor itself before you multiply.

No — they're unrelated units that happen to share a name. The body-weight stone converted here equals 14 lb (6.35029318 kg), used for people, animals, and occasionally produce. Jewelers and gemologists instead measure gemstones in carats, where 1 carat is fixed at exactly 200 milligrams (0.0002 kg) — a unit so much smaller that it takes roughly 31,751 carats to equal a single body-weight stone. The confusion mostly comes from casual phrases like "stone weight" in jewelry listings, which just means "the weight of the gem," not an actual reference to the imperial stone. If you're ever converting a diamond or ruby's weight, you want a carat converter, not this one — the two units differ by more than four orders of magnitude.

Break it into its two parts and convert each separately, then add them. Eleven stone converts at 6.35029318 kg per stone: 11 x 6.35029318 = 69.853225 kg. The remaining 6 lb converts at 0.45359237 kg per pound: 6 x 0.45359237 = 2.721554 kg. Add them together: 69.853225 + 2.721554 = 72.574779 kg, which rounds to 72.57 kg for practical use. This exact figure — 11 st 6 lb — happens to sit close to several combat-sports weigh-in limits, which is why boxing and wrestling commentary sometimes states a fighter's weight in stone-and-pounds for a UK audience right alongside the kilogram figure used in the official record. The two-step math (stone times 6.35029318, plus pounds times 0.45359237) works for any mixed stone-and-pound figure you need to convert.

Because it originally was one — literally, an actual stone used as a counterweight on a balance scale, long before anyone standardized what that stone should weigh. Medieval England had no single "stone": wool merchants used a 14 lb stone, butchers and cheesemongers often used an 8 lb stone, and a stone of glass was fixed at just 5 lb, each trade keeping its own customary reference stone. That patchwork persisted for centuries until the Weights and Measures Act of 1835 formally fixed the imperial stone at 14 lb as the standard for general use, including the emerging habit of describing a person's body weight that way. The 14 lb figure this converter uses today is a direct survivor of that 1835 standardization, not an arbitrary number.

It accepts any decimal value, not just whole stone — enter 11.5 and it multiplies straight through (11.5 x 6.35029318 = 73.028372 kg) exactly the way it would for 11 or 12. That matters because real-world body weight is usually reported as whole stone plus separate pounds (11 stone 7 lb) rather than a decimal stone figure, so if your starting number is in that mixed format, convert the pounds to a decimal fraction of a stone first (7 lb / 14 = 0.5 stone) and enter 11.5 rather than typing 11 and 7 into two different fields. The reference table on this page sticks to whole-stone values for readability, but the live converter itself isn't limited to them.