Jamie steps on the gym scales and reads 80 kg. That evening his mum asks how much he weighs, and she wants the answer in stone, because that is how she has pictured body weight all her life. Turning kg to stone is a sum plenty of British households run every week, and it only takes a minute, provided you avoid one very common slip with decimals.
Quick answer: To convert kg to stone, divide the kilograms by 6.35029318, because one 14 lb stone is exactly 6.35029318 kg. For stones and pounds, multiply whatever follows the decimal point by 14, so 80 kg is 12.60 stone, or 12 stone 8.4 lb, and 12.5 stone is 12 stone 7 lb.
Below you will find the exact factor, Jamie’s conversion worked through line by line, a chart of common weights, a rough method for doing it in your head, and the story of how a unit banned from shop counters in 1985 is still the way most Britons talk about their weight.
In This Guide
What Pound Value Is Behind Every Kg to Stone Conversion?
Every kg to stone conversion traces back to a 1959 agreement that set the international avoirdupois pound at precisely 0.45359237 kg, and 14 pounds make a stone. Every converter, including ours, traces back to an agreement made in 1959. That year a group of English speaking countries settled on a single international avoirdupois pound of precisely 0.45359237 kg. Multiply by 14 pounds and you have the stone, so three figures are worth keeping handy:
- 1 stone = 14 lb = 6.35029318 kg
- 1 kg = about 2.20462 lb
- 1 kg = about 0.157473 stone
So Jamie can split his 80 kg by 6.35029318 to get decimal stone. Using 6.35 on its own is close enough for a bathroom scale reading, since the difference is a fraction of an ounce at normal body weights.
Turning Jamie’s reading into stones and pounds
His mum will not be impressed by “12.6 stone”. She wants something like “12 stone 8”, so Jamie goes the long way round:
- First he changes kilograms into pounds, splitting by 0.45359237 or multiplying by 2.20462.
- Next he splits those pounds by 14 and keeps only the whole number. That is the stones.
- Finally he takes stones × 14 away from his total pounds, and the remainder is the loose pounds.
Jamie at 80 kg
Splitting 80 by 0.45359237 gives 176.37 lb. Over 14, that is 12.598, so 12 full stones. Twelve stones hold 168 lb, and 176.37 less 168 leaves 8.37 lb. Jamie tells his mum he is 12 stone 8.4 lb, and she nods.
His sister at 70 kg
Seventy kilograms makes 154.32 lb. Over 14, that gives 11.02, so 11 stones, which use up 154 lb, leaving 0.32 lb. Strictly she is 11 stone 0.3 lb, though nobody in the family would say anything other than 11 stone.
Why 12.5 stone is not 12 stone 5
This is the slip mentioned at the start. Calculators show tenths, but stones split into 14 pounds rather than 10. Half a stone is therefore 7 lb, which makes 12.5 stone equal to 12 stone 7 lb, not 12 stone 5 lb.
The gap grows towards the top of each stone. Someone whose screen shows 12.9 might write down 12 stone 9 lb, yet 0.9 × 14 is 12.6, so the true figure is 12 stone 12.6 lb, more than 3.5 lb heavier. The fix is always the same: take whatever sits after the decimal point and multiply it by 14, or use a tool that gives stones and pounds straight away.
Quick reference chart
Every kg to stone row below starts from the exact 1959 pound, with the leftover pounds rounded to one decimal place.
| Kilograms | Pounds | Stone (decimal) | Stones and pounds |
|---|---|---|---|
| 50 kg | 110.2 lb | 7.87 st | 7 st 12.2 lb |
| 60 kg | 132.3 lb | 9.45 st | 9 st 6.3 lb |
| 65 kg | 143.3 lb | 10.24 st | 10 st 3.3 lb |
| 70 kg | 154.3 lb | 11.02 st | 11 st 0.3 lb |
| 80 kg | 176.4 lb | 12.60 st | 12 st 8.4 lb |
| 90 kg | 198.4 lb | 14.17 st | 14 st 2.4 lb |
| 100 kg | 220.5 lb | 15.75 st | 15 st 10.5 lb |
| 120 kg | 264.6 lb | 18.90 st | 18 st 12.6 lb |
Doing it without a calculator
Jamie’s sister has a trick for when her phone is out of reach. She doubles the kilograms, adds a tenth of that, and treats the result as pounds before splitting by 14. With 70 kg: doubled is 140, plus 14 is 154, and 154 over 14 is exactly 11 stone. It works because 2.2 sits very close to the true 2.20462. Going the other way, she remembers that each stone is a little over 6.35 kg, so 10 stone lands near 63.5 kg.
Going back from stone to kilograms
Their dad needs kilograms for a hospital pre assessment form. He weighs 12 stone 5 lb, so he multiplies 12 by 6.35029318 to get 76.20 kg, multiplies 5 by 0.45359237 to get 2.27 kg, and adds them for 78.47 kg. Grandma at 9 stone 3 lb comes out at 57.15 kg plus 1.36 kg, which is 58.51 kg. Forms and fitness apps that accept only metric are exactly where our stone to kg converter earns its keep, because it takes stones and pounds together and rounds only once at the end.
Why Is a Stone 14 Pounds?
The 14 pound stone traces to wool, which was given that fixed stone in 1350, and it is the only version of the stone still in use. For most of its life the stone was anything but standard. Two traders in different towns, or selling different goods, could mean quite different weights by the same word. The 14 pound version traces to wool, which was given that fixed stone in 1350, and the history of the stone as a unit records many rival local stones for meat, cheese and other goods. Wool’s version is the only one still in use.
Then came metric. Under the Weights and Measures Act 1985, traders lost the right to sell by the stone, so you will not find a price per stone on any shelf and the scales at your GP surgery read in kilograms. The Act said nothing about how people chat at home, though, and that is where the unit carried on. Many adults raised on stones and pounds still find “11 stone” far easier to picture than “70 kg”.
Britain is relaxed about mixing systems. Distances on road signs are in miles, beer is poured in pints, and drivers still judge cars by miles per gallon while filling up in litres, which is why our L/100km to mpg converter sits next to the weight tools on this site. The stone fits that pattern: metric on paper, imperial at the kitchen table.
How Many Kilograms Is One Stone?
One stone equals 6.35 kg, so a target of losing a stone from a starting weight of 95 kg is reached at 88.65 kg. Jamie’s dad has set himself a target of losing a stone. Swapping between units week to week invites rounding errors, so he logs everything in kilograms and only converts when someone asks. His target is simple to express either way: one stone equals 6.35 kg. Starting from 95 kg, he will hit it at 88.65 kg. To see that change as a share of his starting weight, which is a fairer way to compare progress, he runs both numbers through our percentage difference calculator.
Key points
- A pound is fixed at 0.45359237 kg, so a 14 lb stone is 6.35029318 kg.
- Split kilograms by 6.35029318 for decimal stone: 80 kg gives 12.60 st.
- Multiply whatever follows the decimal point by 14 to find the loose pounds.
- Shops and clinics have used kilograms since 1985, but stone lives on for body weight.
Frequently Asked Questions
My gym app wants kilograms. What do I enter for exactly one stone?
Enter 6.35 kg. The precise figure is 6.35029318 kg, which comes from 14 pounds of 0.45359237 kg each.
The nurse said I weigh 75 kg. What is that in stone and pounds?
Seventy five kilograms makes 165.35 lb. Eleven stones account for 154 lb, leaving 11.35 lb, so you are about 11 stone 11.3 lb.
My scales show 12.5. Should I write 12 stone 5 in my diary?
No, write 12 stone 7. Half of a 14 pound stone is 7 lb, so multiply the 0.5 by 14 rather than reading it as pounds.
My American friend has never heard of stone. Is it only British?
Pretty much. People in the UK and Ireland use it, mainly for body weight. Americans quote pounds only, so 12 stone would be 168 lb to them, and most other countries use kilograms.
Jamie’s mum got her answer, his dad has a target in both units, and the whole family now multiplies the decimal by 14. Start from the exact factor and handle the leftover pounds properly, and your figure will agree with any clinic scale, whichever unit you think in.