Stone to Kilograms Converter

Stone to Kilograms — The Fast Answer

To convert stone to kilograms, multiply the stone value by 6.35029318. So 1 st = 6.35 kg, 10 st = 63.50 kg, 12 st = 76.20 kg, and 15 st = 95.25 kg. If your weight is in stones and pounds (for example, 11 st 4 lb), first turn it into total pounds using (stones × 14) + pounds, then multiply by 0.453592 to get kilograms.

What Is Stone to Kilograms Conversion?

Stones and kilograms measure the same thing — weight — but they come from two very different worlds. The stone is an old imperial unit that has quietly survived in everyday British and Irish life, while the kilogram is the modern, scientific standard used in almost every country and every lab on the planet. Converting between the two doesn't change how heavy something is; it just changes the language used to describe it.

This conversion comes up more than you'd think. A UK adult stepping on a digital scale that defaults to kilos, a nurse entering a patient's weight into an NHS system, a traveller filling in a medical declaration for a long-haul flight, a parent comparing a baby's weight on a Canadian growth chart — all of them need a quick, accurate way to move between stone and kg.

The relationship between the two units is fixed and exact: 1 stone = 6.35029318 kilograms, which is the same as saying 1 kilogram ≈ 0.157473 stone. That number isn't a rounded approximation — it's defined by the international pound (0.45359237 kg) multiplied by 14, since a stone is exactly 14 pounds.

The Stone (st)

The stone is one of those units that refuses to retire. Originally used across medieval Europe for weighing trade goods — wool, cheese, potatoes — it settled at exactly 14 pounds in Britain in 1835. It was officially removed from UK trade use in 1985, but you'll still hear it everywhere: at the GP, in slimming clubs, on the bathroom scales, and in casual conversation. "I'm about twelve stone" sounds completely normal in Manchester; "I weigh 76 kilograms" does not.

The Kilogram (kg)

The kilogram is the base unit of mass in the International System of Units (SI) and the only SI unit still named with a prefix ("kilo" meaning one thousand grams). Until 2019 it was defined by a single platinum-iridium cylinder kept in a vault near Paris. Since May 2019 it has been redefined using Planck's constant — a fundamental value from physics — meaning the kilogram is now tied to the laws of nature rather than a physical object that could drift over time.

How to Convert Stone to Kilograms

The core formula is straightforward: multiply the stone value by 6.35029318. The result is your weight in kilograms.

Stones and Pounds to Kilograms

Most UK adults don't think in whole stones — they think in stones and pounds, like "nine stone seven" or "14 st 3 lb". For that format, the cleanest approach is a two-step conversion: turn everything into pounds first, then convert once to kilograms.

Which Conversion Factor Should You Use?

You'll see different numbers floating around online — 6.35, 6.3503, 6.35029, 6.35029318. They're all the same factor at different levels of precision. For everyday weight chat, 6.35 is fine. For medical notes, a dosage calculation, or any context where the answer feels official, use the full 6.35029318 — it comes straight from the international definition of the pound and carries almost no rounding error.

The Reverse: Kilograms to Stones

Going the other way? Multiply kilograms by 0.157473, or simply divide by 6.35029318. Our kilograms to stone converter handles this automatically, including the decimal-to-pounds step so you can read the result in the familiar UK "X st Y lb" style.

Common Stone to Kilograms Values

Here are the most-searched stone-to-kg conversions in one place. The table includes whole stones plus the common half-stone milestones that show up in weight-loss tracking and BMI checks.

Every extra whole stone adds exactly 6.35029 kg, so once you've memorised a couple of anchor values (like 10 st = 63.5 kg and 14 st = 88.9 kg), you can estimate anything in between in your head. Need the pounds equivalent too? See our stone to pounds converter, or use pounds to kilograms if your starting value is already in pounds.

How to Convert Stone to Kilograms in 3 Easy Steps

If you're doing the maths by hand — on the back of an envelope, say, or checking a printed chart — this is the fastest reliable method.

1. 1
   Write down your weight in stones (and pounds, if any)

   Let's use 12 st 4 lb as a worked example. If you've already got a clean decimal like 12.5 st, you can skip straight to step two — just multiply by 6.35029318. For the stones-and-pounds format, first combine them into a single pound total: (12 × 14) + 4 = 172 lb.

2. 2
   Multiply by the right conversion factor

   For whole stones: kg = st × 6.35029318. For total pounds: kg = lb × 0.453592. In our example, 172 × 0.453592 = 77.9978 kg.

3. 3
   Round sensibly and write the unit

   For an everyday answer, round to one decimal place: 78.0 kg. For a medical or technical form, two decimals is usually ideal: 78.00 kg. Always include "kg" so nobody mistakes it for pounds.

A Quick Mental Estimate

Don't need perfect accuracy? Multiply stones by 6.35 and ignore the longer decimal. 11 st × 6.35 = 69.85 kg. 14 st × 6.35 = 88.9 kg. Even simpler: multiply stones by 6, then add roughly 5% — close enough for a chat in the pub or a quick gym estimate.

FAQ

Frequently Asked Questions

The questions people most commonly search for around stone-to-kilogram conversion.

Everyday Uses for Stone to Kilograms Conversion

This isn't just a maths exercise. Stone-to-kg conversion is quietly doing work in the background of dozens of everyday situations, especially when British habits meet international standards.