A metric carat is exactly 200 milligrams.
Carats to Stones Converter — ct to st
Convert Carat (ct) to Stone (st) using the exact conversion factor (1 carat = 0.0000314946 stone). See the formula, worked examples, conversion table, history, and common uses.
Carats to Stones converter
Converter
Mass/Weight Converter
Convert SI mass, imperial weight, jewelry, atomic, and astronomy mass units.
Context values
Some unit families need one extra value for a physically accurate result.
A stone is 14 pounds.
Result = input x 0.0002 / 6.35029318.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Carats to Stones
Weight conversions between Carat and Stone come up constantly in everyday commerce, shipping, and cooking, since US packaging is usually labeled in pounds while most of the rest of the world uses kilograms. Specifically: A metric carat is exactly 200 milligrams, and a stone is 14 pounds.
Formula
stones = carats × 0.0000314946088836
This factor comes from each unit's defined relationship to the category's base unit: 1 carat equals 0.0002 base units, and 1 stone equals 6.35029318 base units, so dividing one by the other gives the direct carat-to-stone factor of 0.0000314946088836.
Simple example
1 ct × 0.00003149460888 = 0.0000314946 st
1 carat = 0.0000314946 stones.
Real-world example
50 ct × 0.00003149460888 = 0.0015747304 st
50 carats = 0.0015747304 stones.
Conversion table
| Carat (ct) | Stone (st) |
|---|---|
| 1 ct | 0.0000314946 st |
| 5 ct | 0.000157473 st |
| 10 ct | 0.0003149461 st |
| 25 ct | 0.0007873652 st |
| 50 ct | 0.0015747304 st |
| 100 ct | 0.0031494609 st |
Reverse conversion: Stone to Carat
0.0000314946 st × 31751.4659 = 0.9999997179 ct
0.0000314946 stones = 0.9999997179 carats.
carats = stones × 31751.4659
For a page dedicated to this direction, see Stone to Carat.
Understanding the Carat (ct)
A metric carat is exactly 200 milligrams.
Understanding the Stone
Stone (st) measures mass. A stone is 14 pounds: exactly 6.35029318 kilograms. It is classified as a UK customary unit.
Where it's used: United Kingdom and Ireland (body weight)
Uses of the Stone today
- Body weight reporting in the UK and Ireland (e.g. '12 stone 5 pounds')
- Historical wool and agricultural produce weighing
History of the Stone
The stone dates to medieval England as a general-purpose weight unit, historically varying by region and commodity (a 'stone' of wool differed from a 'stone' of meat) before settling on 14 pounds for general use. It remains in everyday use for body weight in the UK and Ireland, unlike most other English customary units which have been replaced or supplemented by metric measures.
Historical origin. Stone was not the invention of a single named person; it developed through the process described above.
Stone — sources
- UK Weights and Measures Act 1985 — Confirms the stone (14 lb) as a legally recognized UK unit for body weight.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many stones are in 1 carat?
1 carat equals 0.0000314946 stones, using the exact defined conversion factor rather than an estimate.
How do I convert carat to stone?
Multiply the carat value by 0.00003149460888. The converter above does this instantly to whatever precision you set.
How do I convert stone back to carat?
Use the reverse factor: 1 stone equals 31,751.4659 carats. You can also use the swap control in the converter above to flip the direction instantly.
What is a carat?
Carat (ct) is a unit of mass/weight.
What is a stone?
Stone (st) measures mass. A stone is 14 pounds: exactly 6.35029318 kilograms. It is classified as a UK customary unit.
Is the carat to stone conversion exact?
Yes. A stone is 14 pounds: exactly 6.35029318 kilograms. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.