Article — Stone to Lbs Converter
Stone to lbs: the British weight unit that won't go away
One stone equals exactly 14 pounds, or 6.35029 kilograms. The factor has been fixed since the UK Weights and Measures Act of 1835. To convert stone to lbs, multiply by 14. To go the other way, divide pounds by 14 — the remainder is the leftover pounds in a mixed reading.
The converter at the top of this page does the math in either direction, with quick picks for the body-weight range that gets searched the most (1, 5, 8, 10, 12, 15, 20 stone). The article covers where the unit came from, why the UK still uses it, and how to read mixed stone-and-pounds without getting tripped up.
What is a stone?
A stone is a unit of mass equal to 14 pounds, or roughly 6.35 kilograms. The symbol is "st." It is the standard unit of body weight in the United Kingdom and Ireland in everyday speech — even when official medical and gym records have switched to kilograms. The stone is not part of the metric system, but UK law recognises it under the Weights and Measures Act of 1985 for "supplementary" use.
The unit name comes from the literal stones once used as reference weights at market. A merchant kept a calibrated rock, and "one stone of wool" meant whatever the rock weighed when the local guild signed it off. Different goods used different stones for centuries — wool at 14 pounds, glass at 5 pounds, fish at 8 pounds in some regions — until 1835 standardised the 14-pound stone for everything.
Before 1835, the British "stone" varied so widely that contracts had to specify the goods. A "stone of wool" was 14 lbs but a "stone of glass" was 5 lbs, a "stone of meat" was 8 lbs in many regions, and a "stone of sugar" could run as high as 16 lbs. The Weights and Measures Act of 1835 declared the 14-pound stone the only legal version, and that wool-trade convention is the one still in use today.
The stone to lbs formula
To convert stone to pounds, multiply by 14. To convert pounds to stone, divide by 14. There is no measurement uncertainty in either direction — the factor is a legal definition, not a physical observation.
stone × 14 = lbslbs ÷ 14 = stone (decimal)lbs ÷ 14 = stone rem lb = mixed formatstone × 6.35029 = kgThe kilogram link goes through the pound. One pound is 0.45359237 kg by the 1959 International Yard and Pound Agreement, so one stone is 14 × 0.45359237 = 6.35029318 kg exactly. Six decimals of precision is enough for any practical purpose — a 75 kg adult is 11.81 stone, or 11 stone 11 pounds in the mixed format.
Common stone to lbs conversions
The conversions used most often, computed at the exact 14× factor:
- 1 stone = 14 lbs (6.35 kg) — a bag of self-raising flour
- 5 stone = 70 lbs (31.8 kg) — small child
- 8 stone = 112 lbs (50.8 kg) — small adult
- 10 stone = 140 lbs (63.5 kg) — UK women's average
- 11 stone = 154 lbs (69.9 kg) — median UK adult
- 12 stone = 168 lbs (76.2 kg) — UK men's average
- 14 stone = 196 lbs (88.9 kg) — large adult
- 16 stone = 224 lbs (101.6 kg) — heavy adult
- 20 stone = 280 lbs (127 kg) — heavyweight
Stone to lbs for body weight
Stone is the unit a British person will use to describe their own weight in conversation. "I'm 12 stone 4" means 12 × 14 + 4 = 172 pounds, or 78 kilograms. The mixed-format reading — stone-and-pounds — is the way UK bathroom scales display the number. The decimal-stone reading shows up only in spreadsheets.
To split a pound count into stone-and-pounds, divide by 14 and keep the remainder. 175 lbs ÷ 14 = 12 remainder 7, so 175 lbs = 12 stone 7. The remainder is always 0 to 13, because at 14 you roll over into the next stone. A reading of "11 stone 14" would be wrong — that's 12 stone 0.
UK health bodies have largely switched to kilograms in clinical records, but patient-facing communication still leans on stone. The NHS BMI calculator accepts inputs in stone or kilograms. Pharmacies and dietitians will often ask for weight in stone first and convert internally. Even gym scales sold in the UK display all three units side by side.
Stone to lbs in boxing and horse racing
British boxing posts class limits in stone-and-pounds, even though the international rules use pounds and kilograms. A welterweight fighter must weigh 10 stone 7 pounds or less — that's 147 lbs, or 66.7 kg. A middleweight is capped at 11 stone 6 (160 lbs). Cruiserweight is 14 stone 4 (200 lbs). Above that, you're a heavyweight with no upper limit.
Horse racing uses stone even more strictly. Jockeys must "make weight" before every race — flat-race jockeys at a minimum of 7 stone 12 (110 lbs), jump-race jockeys at 10 stone (140 lbs) and up. The handicap system adds extra weight to faster horses, also in stone-and-pounds, to even out the field. Saddle and gear are weighed in, so the jockey's body weight runs a few pounds below the posted figure.
To check a UK boxing weight class against a US fighter's pound listing, multiply the stone-and-pounds: middleweight = 11 × 14 + 6 = 160 lbs. The result matches the US WBA and WBC class names that also use pounds, because both systems were harmonised in the early 20th century.
A short history of the stone
The stone goes back to early medieval Europe, when literal stones served as weight references at markets. England's earliest mentions trace to the 13th century, by which point a "stone of wool" was 14 pounds. The exact weight kept drifting through the 16th and 17th centuries — different counties, different goods, different stones.
The 1824 Weights and Measures Act consolidated British units but did not pin down the stone. That came in 1835, when an amending act declared the legal stone to be 14 pounds for all trade purposes. Within a generation, the wool-trade convention became the only stone in legal use. Other countries — France, the German states, Italy — had abandoned local "stones" for the metric kilogram by the 1870s.
Mental math: stone to lbs in your head
The ×14 multiplication is awkward for mental math, but it splits cleanly into ×10 and ×4. Take the stone number, multiply by 10, then add four times the stone number. 12 stone → 120 + 48 = 168 lbs. 9 stone → 90 + 36 = 126 lbs. 15 stone → 150 + 60 = 210 lbs.
For the reverse, the trick is to spot multiples of 14. 70 lbs = 5 stone, 140 lbs = 10 stone, 168 lbs = 12 stone, 196 lbs = 14 stone, 224 lbs = 16 stone. Anything between two anchor points splits into the stone count plus a remainder of 0 to 13 pounds.
To go from stone to kilograms, multiply by 6 and add a third of the stone count. 10 stone → 60 + 3.3 = 63.3 kg (true value 63.5 kg, off by 0.3%). 15 stone → 90 + 5 = 95 kg (true 95.25). The shortcut underestimates by half a percent, fine for everything except dosage and competition weigh-ins.
Common stone to lbs mistakes
- "14 stones" with a number — wrong in spoken UK English. The singular form is invariant after a number: "14 stone," not "14 stones."
- Pounds rolling over — 11 stone 14 is the same as 12 stone 0. The pounds part of a mixed reading is always 0 to 13.
- Stone confused with kg — telling a non-UK doctor "I weigh 12 stone" without unit context can be read as 12 kg. The five-fold gap matters.
- US to UK conversion — Americans use lbs only. Telling an American "I'm 11 stone 7" will get a blank look. Convert to 161 lbs first.
- Decimal vs mixed — 11.5 stone is not 11 stone 5 pounds. 11.5 stone is 11 stone 7 pounds (0.5 × 14 = 7).
- Old goods-specific stones — pre-1835 historical sources may quote weights in goods-specific stones (5, 8, or 16 lbs). Always check the era and goods.