Stone to Pounds Converter

What is a stone, and why 14 pounds?

A stone (symbol st) is a British unit of mass used almost exclusively for one thing today: body weight. It is defined as exactly 14 pounds:

• 1 stone = 14 lb exactly
• 1 stone = 6.35029318 kg
• 1 lb = 0.0714286 stone (1 ÷ 14)

Formulas:

• pounds = stone × 14
• stone = pounds ÷ 14

Worked example: a person who weighs 12 stone is 12 × 14 = 168 pounds, which is 168 × 0.45359237 = 76.20 kg. Someone at 10 stone is 140 lb (63.50 kg). The stone survives in the UK and Ireland because people think of body weight in half-stones (7 lb) and stones; the number is compact, "12 stone" instead of "168 pounds."

The arithmetic is deliberately simple: 14 is an easy multiplier and divisor, so stone-to-pound conversions can be done mentally. The only complication is the two-part shorthand British speakers use, where "12 stone 7" adds seven pounds on top of the twelve stone.

Why the stone is 14 pounds, the legal history

The stone was not always 14 pounds. Historically it varied by trade and region, a "stone" of wool, of beef or of hay could mean different weights. The value was standardized for trade in Britain over the nineteenth century, and the Weights and Measures Act 1985 still defines the stone at 14 pounds in UK law. The pound-to-kilogram relationship behind it is fixed by NIST Special Publication 811, which lists 1 lb = 0.45359237 kg exactly.

This matters because the stone is one of the few pre-metric units the UK kept for everyday personal use. When Britain began metrication in the 1960s, body weight in stones survived in conversation and on bathroom scales even as groceries, fuel and most goods moved to metric. Today UK hospitals may record weight in kilograms, but patients and newspapers still say "he weighs 15 stone." The US never adopted the stone at all. Americans go straight from pounds to a decimal, which is why a US reader meeting "12st 7lb" needs a converter.

Stone to pounds reference table (and kilograms)

Multiply stone by 14 for pounds, then multiply pounds by 0.45359237 for kilograms.

Numeric check: 12 stone = 168 lb = 76.204 kg (12 × 14 = 168; 168 × 0.45359237 = 76.2035) and 15 stone = 210 lb = 95.254 kg. Note that 14 stone equals 196 lb, not 200, a common mental slip.

Use the kilogram column as a cross-check: 1 stone is 6.35 kg, so 2 stone is 12.70 kg, 5 stone is 31.75 kg and 10 stone is 63.50 kg. Every extra stone adds about 6.35 kg, so a 3-stone change is roughly 19 kg.

Reading "12 stone 7", the st/lb shorthand

British body weight is often written in a two-part shorthand: "12 stone 7" or "12st 7lb" means 12 stone plus 7 pounds. That is 12 × 14 + 7 = 175 lb (79.38 kg). Because a stone is 14 lb, the trailing number runs from 0 to 13 and then rolls over, you never see "12 stone 14," because that is 13 stone.

Practical reading:

• "10 stone 2" = 10 × 14 + 2 = 142 lb (64.41 kg)
• "13 stone 4" = 13 × 14 + 4 = 186 lb (84.37 kg)
• "9 stone 10" = 9 × 14 + 10 = 136 lb (61.69 kg)

If you are tracking a diet with a scale that reports only pounds, the shorthand is the thing to convert. A half-stone is 7 lb (3.18 kg), which is why "I lost half a stone" is a common way to say "I lost 7 pounds."

Common stone-to-pounds mistakes

These errors show up constantly when Americans read UK weights:

• Assuming a stone is 10 or 16 lb. It is 14 lb exactly, not 16 (that is the old "stone" of some trades) and not 10.
• Ignoring the trailing pounds. "12 stone 7" is 175 lb, not 168 lb. Dropping the "7" loses half a stone.
• Converting stone to kg by a wrong factor. Go stone → lb (×14), then lb → kg (×0.45359237). Do not invent a direct stone-kg factor from memory.
• Treating the stone as US. It is a British/Irish unit; US body weight is in pounds only.

Rule of thumb: 1 stone = 14 lb, so a 4-stone change is 56 lb. For a quick kg estimate, remember 1 stone ≈ 6.35 kg.

A final check: a stone is not a decimal of a pound but a whole separate unit, so never write "12.7 stone" when you mean 12 stone 7 lb, those are different weights (12.7 stone is 177.8 lb, while 12 stone 7 is 175 lb).

Body weight in context: stones, pounds and kilograms

Because the stone is 14 lb and the kilogram is 2.20462 lb, British, American and metric body weights are three views of the same number:

• 12 stone = 168 lb = 76.20 kg
• 13 stone = 182 lb = 82.55 kg
• 14 stone = 196 lb = 88.90 kg
• 16 stone = 224 lb = 101.60 kg

Two worked checks: someone who weighs 11 stone 4 is 11 × 14 + 4 = 158 lb, which is 158 × 0.45359237 = 71.67 kg. A US scale reading 180 lb is 180 ÷ 14 = 12.86 stone, or 12 stone 12 lb (0.857 × 14 = 12.0). Because a pound is 0.45359237 kg, the same person reads a bigger number in pounds than in kilograms and a smaller number in stones than in either, a 76 kg adult is 168 lb is 12 stone.

UK hospitals and GPs increasingly record weight in kilograms while patients and newspapers still speak in stones, so a doctor's "82 kg" and a patient's "13 stone" describe the same body. For anything medical, medication dosing, BMI, fitness tracking, convert to kilograms, because the clinical formulas are written in metric.

Quick mental conversions for stones and pounds

Two anchors make stone-and-pound math fast:

• stone to pounds: multiply by 14. Ten stone is 140 lb, twelve stone is 168 lb, fifteen stone is 210 lb.
• pounds to stone: divide by 14. A 154 lb reading is 154 ÷ 14 = 11 stone exactly.

A half-stone is 7 lb and a quarter-stone is 3.5 lb, so body-weight changes are often spoken in halves: "down half a stone" means down 7 lb. Worked example: a scale showing 182 lb is 182 ÷ 14 = 13.0 stone, or 13 stone 0. A scale showing 165 lb is 165 ÷ 14 = 11.79 stone, which is 11 stone 11 lb (0.79 × 14 = 11.0). To jump straight to kilograms, multiply pounds by 0.45359237: 182 lb is 82.55 kg. The stone is a compact way to say a large pound number, which is exactly why it survives in British body-weight conversation.