What Is Carat?
One carat equals 0.2 grams, and it is divided into 100 points, so a 0.50 carat stone is also called a 50-point stone. Carat measures weight, not diameter or length.
Two stones with the same carat weight can look different, because shape, cut, and proportions change how the weight is spread.
Carat and Visual Size
A round stone grows in diameter as carat increases, but not in a straight line. Doubling the weight does not double the diameter, because weight grows in three dimensions.
| Carat weight | Typical round diameter |
|---|---|
| 0.50 | About 5.1 mm |
| 0.75 | About 5.8 mm |
| 1.00 | About 6.5 mm |
| 1.50 | About 7.4 mm |
| 2.00 | About 8.1 mm |
How Carat Affects Price
Price rises faster than weight, because larger rough stones are rarer. Stones just below a whole number, such as 0.90 instead of 1.00, often cost noticeably less for a very small size difference.
Cut and shape also affect price at the same weight. A well-cut stone can look larger and brighter than a poorly cut stone that weighs more.
How to Choose a Carat Weight
Decide a size range first, then compare cut and shape within that range. Consider the wearer hand size, the setting style, and how the stone will look next to a wedding band.
If your budget is tight, a slightly smaller, well-cut stone usually looks better than a larger, poorly cut stone at the same price.
Diamond Carat Guide FAQ
Does carat mean size?
Carat is weight. Size also depends on shape, cut, and proportions, so two stones of the same weight can look different.
What is a good carat weight for an engagement ring?
There is no single answer. Consider hand size, setting, lifestyle, and budget, and compare stones in person when you can.
Is a 1.00 carat stone much bigger than 0.90?
The diameter difference is small, usually under half a millimeter, while the price difference can be large.
Does carat affect sparkle?
Indirectly. A larger stone has more facets to return light, but cut has a bigger impact on sparkle than weight alone.
What are points?
One carat is divided into 100 points. A 0.75 carat stone is a 75-point stone.