The numbers
One carat (ct) is exactly 0.2 g, or 200 mg, so 5 carats make 1 gram. The metric carat has been the international standard for diamonds and other gemstones since 1913.
| Carats | Grams |
|---|---|
| 0.25 | 0.05 |
| 0.5 | 0.1 |
| 1 | 0.2 |
| 2 | 0.4 |
| 5 | 1 |
Points
Jewellers divide a carat into 100 points. One point is 0.01 carat, or 2 mg. A “50-pointer” is a half-carat stone.
Weight, not size
A carat measures how heavy a stone is, not how wide. Two stones of the same carat weight can look different sizes if they are different materials or cuts. Don’t confuse it with karat, which measures gold purity.