Kilograms to Stones and Pounds Converter

What this converter does

It expresses a metric weight in the two-part form used for body weight in the United Kingdom and Ireland: whole stones, then pounds. A hospital letter or gym record may say 73.4 kg; the person it describes almost certainly thinks of themselves as “eleven and a half stone”. This page does the translation in one step, without the intermediate decimal-stones figure that no one actually uses.

How the conversion works

Two exact constants and one split. Kilograms are first converted to total pounds by dividing by 0.45359237 (the exact 1959 definition of the pound). The whole stones come out of that total — one stone is exactly 14 pounds — and whatever remains under 14 is the pounds part. For 70 kg: 70 ÷ 0.45359237 = 154.3236 lb; 154.3236 ÷ 14 = 11 remainder 0.3236; so 70 kg is 11 st 0.3 lb. Only that final remainder is rounded, at the precision you choose, which is why the stones figure can never be off by one.

The rounding control matters more here than on most converters. Rounded to whole pounds, 79.9 kg reads 12 st 8 lb; at one decimal it reads 12 st 8.1 lb. Bathroom scales showing st/lb typically round to the nearest whole pound or quarter pound, so if you are comparing against a scale, match its coarseness rather than trusting extra digits neither of you measured.

Worked examples

70 kg → 11 st 0.3 lb, the reference adult weight in metric countries landing almost exactly on eleven stone. 63.5 kg → exactly 10 st 0 lb, because 63.5029318 kg is the exact value of ten stone — a coincidence worth noticing, since “I’m ten stone” and “I’m 63.5 kilos” are the same claim to within 3 grams. 100 kg → 15 st 10.5 lb. A newborn at 3.5 kg → 0 st 7.7 lb, which is why babies get pounds-and-ounces rather than stones: the stones digit is always zero.

Why Britain weighs people in stones

The stone was a genuine trade unit for centuries — wool, meat and potatoes moved in stones of various regional sizes until the 14 lb stone was standardised. Metrication removed it from commerce (it ceased to be lawful for trade in 1985) but never from self-description: body weight in Britain and Ireland is culturally denominated in stones, full stop. The result is a unit that exists almost nowhere else and for almost nothing else, which is precisely why this two-part converter exists — no American scale shows it, and no metric document records it.

Reading the result against NHS charts and scales

Printed reference charts round twice, first to whole pounds and often again to quarter stones, so a chart can legitimately sit a pound from this page’s answer without either being wrong — the chart is just coarser. Digital UK scales vary in their internal rounding too; a scale showing 11 st 4 lb may hold anything from about 71.4 to 71.9 kg. When a difference matters — medication dosing, competitive weigh-ins — the kilogram figure is the primary measurement and the stones form is presentation.

Common mistakes

The classic is treating the pounds part as decimals: writing 11 st 4 lb as 11.4 stones. It is actually 11 + 4/14 = 11.286 st, and the error grows with the pounds figure — 11 st 13 lb is nearly 12 stone, not 11.13. This converter exists so that arithmetic never happens by hand. The second mistake is a fourteen in the pounds place: “10 st 14 lb” is not a weight, it is 11 stone written wrongly, and the tool will always carry it rather than display it. Third, converting a stones figure through an ounces path — stones break into pounds (14) and pounds into ounces (16), and mixing the two ratios mid-calculation produces confidently wrong answers.

Benchmarks

50 kg = 7 st 12.2 lb. 60 kg = 9 st 6.3 lb. 63.5 kg = 10 st 0 lb. 70 kg = 11 st 0.3 lb. 76.2 kg = 12 st 0 lb. 80 kg = 12 st 8.4 lb. 88.9 kg = 14 st 0 lb — one stone of stones, as it were. 100 kg = 15 st 10.5 lb. 127 kg = 20 st 0 lb. The exact-stone values recur every 6.35029318 kg, which is the stone’s exact metric size.

Accuracy and limits

Both constants in the chain are exact definitions, so the split itself is exact; the displayed pounds remainder is the only rounded quantity, and you choose its precision. The converter accepts any non-negative value, including ones far outside human range — it will cheerfully report a 1,000 kg piano as 157 st 6.9 lb — but stones are a body-weight idiom, and for goods that size the tonnes and hundredweight pages linked below speak the trade’s actual language. What this page will not do is interpret weight medically: it converts numbers faithfully and leaves what they mean to you and, where it matters, your clinician.

Tracking a changing weight in two systems

Weight goals bought in one unit get measured in the other constantly: a plan says lose half a kilo a week, the scale speaks stones. Half a kilogram is 1.10 lb, so a steady 0.5 kg weekly loss shows up as roughly a pound a week on a stones scale — and a whole stone, 6.35 kg, is about thirteen weeks at that rate. Running the arithmetic in kilograms and converting for display keeps the trend honest, because the st/lb form quantises to the scale’s rounding and can show a flat week that was actually a 0.4 kg loss.

Where stones still rule beyond the bathroom

Two professions never metricated their body weights: British and Irish horse racing, where jockeys’ allocated weights are set in stones and pounds and a rider “does 8 st 7” as a term of art, and boxing in the UK, where the traditional weight classes carry stone names — the 12 st 7 lb light-heavyweight limit, for instance — alongside the kilogram figures used by international bodies. Anyone reading a race card or an old fight record needs exactly this page’s conversion, in this direction, which is part of why the two-part format refuses to die.