Stones to Carats
An instant stones-to-carats converter, with the formula and a reference table below.
| Stones | Carats |
|---|---|
| 1 st | 31751.4659 ct |
| 2 st | 63502.9318 ct |
| 3 st | 95254.3977 ct |
| 5 st | 158757.3295 ct |
| 10 st | 317514.659 ct |
| 25 st | 793786.6475 ct |
| 50 st | 1587573.295 ct |
| 100 st | 3175146.59 ct |
How to use
- Enter a value in the Stones field.
- The Carats figure appears immediately — no button to press.
- Typing in the Carats field converts back to Stones the same way.
- Use the reference table for the values that come up most often.
Stones to Carats formula
The factor from stones to carats is 31751.4659.
ct = st × 31751.4659
Why this factor: the stone and the carat are both defined against the kilogram, so dividing one definition by the other gives 31751.4659 directly. Both definitions are set out in full below.
To go the other way, divide by 31751.4659 — or use the Carats to Stones converter, which is the same calculation reversed.
Worked example
Take 150 st and multiply by the factor 31751.4659: the result is 4762719.885 ct.
150 st × 31751.4659 = 4762719.885 ct
The converter above does this for any value you type, in either direction.
What is a stone?
A stone is fourteen pounds, still the customary unit for body weight in Britain and Ireland.
Definition: Fourteen avoirdupois pounds, so exactly 6.35029318 kilograms.
Where it is used: Personal body weight in the UK and Ireland, where weight is usually given as stones and pounds.
Worth knowing: Effectively unused in the United States, where body weight is quoted in pounds alone.
What is a carat?
A metric carat is the standard mass unit for gemstones.
Definition: Exactly 200 milligrams — that is, 0.2 gram — standardized internationally in 1907.
Where it is used: Diamond and gemstone weight throughout the jewellery trade.
Worth knowing: Do not confuse the carat (gemstone mass) with the karat (gold purity out of 24). A 1-carat diamond and 24-karat gold measure entirely different things.
Stones vs Carats
The stone is an imperial unit while the carat is a specialized unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many carats are in a stone?
One stone equals 31751.4659 carats.
What is the formula to convert stones to carats?
Multiply the number of stones by 31751.4659. To reverse it, divide by 31751.4659 instead.
How do I convert carats back to stones?
Divide by 31751.4659, which is the same as multiplying by 3.14946089e-05.
How many carats are in 10 stones?
10 st works out to 317514.659 ct.
Is there anything to watch out for with stones?
Effectively unused in the United States, where body weight is quoted in pounds alone.
How is the stone defined?
Fourteen avoirdupois pounds, so exactly 6.35029318 kilograms.