Diamond Carat Size Chart: How Big Each Carat Weight Really Is
Carat is weight, not size. This diamond carat size chart shows the typical diameter of a round diamond from 0.25 to 5 carats, the size of a 1 carat diamond in ten shapes, and why a diamond just under a round number can save a lot.
By Rafi Mizrahi, diamond dealer for 26 years
A carat is a unit of weight: one carat is 0.2 grams. How big a diamond looks depends on its shape and how it was cut, not only its weight. Two 1-carat rounds can differ in diameter by a few tenths of a millimeter, and a 1-carat oval looks larger face-up than a 1-carat round. Carat is one of the 4Cs, and it has the biggest single effect on price.
Round Diamond Carat Size Chart
Typical diameters for well-cut round brilliants:
| Carat | Diameter | Compared with 1 carat (face-up area) |
|---|---|---|
| 0.25 ct | 4.1 mm | About 40% |
| 0.50 ct | 5.1 mm | About 64% |
| 0.75 ct | 5.8 mm | About 82% |
| 1.00 ct | 6.4 mm | — |
| 1.25 ct | 6.9 mm | About 1.2× |
| 1.50 ct | 7.4 mm | About 1.3× |
| 2.00 ct | 8.1 mm | About 1.6× |
| 2.50 ct | 8.8 mm | About 1.9× |
| 3.00 ct | 9.3 mm | About 2.1× |
| 4.00 ct | 10.2 mm | About 2.5× |
| 5.00 ct | 11.0 mm | About 3× |
Size doesn't grow in step with weight. A 2-carat round weighs twice as much as a 1-carat round but is only about 27% wider, with about 60% more surface face-up. Price, on the other hand, grows faster than weight: a 2-carat diamond usually costs much more than two 1-carat diamonds of the same grades, because larger rough is rarer.
1 Carat Diamond Size by Shape
Typical face-up dimensions of a 1-carat diamond in each shape:
| Shape | Typical size at 1 carat | Looks next to a 1 ct round |
|---|---|---|
| Round | 6.4 mm | — |
| Oval | 7.7 × 5.7 mm | Larger |
| Pear | 8.5 × 5.5 mm | Larger |
| Marquise | 10.0 × 5.0 mm | Larger |
| Emerald | 7.0 × 5.0 mm | About the same, longer |
| Radiant | 6.5 × 5.0 mm | Slightly smaller |
| Cushion | 5.5 × 5.5 mm | Smaller |
| Princess | 5.5 × 5.5 mm | Smaller |
| Asscher | 5.5 × 5.5 mm | Smaller |
| Heart | 6.5 × 6.5 mm | About the same |
Elongated shapes spread more of their weight across the top, which is why ovals, pears and marquises look bigger for the money. Square shapes keep more weight in their depth. Our diamond shapes guide compares how each one looks and costs.
Magic Sizes: Why 0.90 Carat Can Be the Smart Buy
Prices jump at round numbers that buyers ask for: 0.50, 0.70, 0.90, 1.00, 1.50, 2.00 and 3.00 carats. A 0.95-carat diamond is about 0.1 mm smaller across than a 1.00-carat diamond, which nobody can see once it's set, but it often costs noticeably less. The same goes for 1.40 vs 1.50 and 1.90 vs 2.00. If the number on the paper doesn't matter to you, buying just under a magic size is one of the easiest ways to save. Try it in the diamond price calculator: change the carat from 0.95 to 1.00 and watch the price.
Depth Changes How Big a Diamond Looks
Two diamonds of the same weight can face up at different sizes. A diamond cut too deep hides weight underneath, so a 1-carat round with a depth of 65% may measure 6.2 mm instead of 6.4 mm, the size of a 0.90-carat diamond. Compare the measurements on the report, not just the carat weight. The diamond cut chart lists the proportions that face up well.
How It Looks on the Hand
On a ring, size is relative. The same diamond looks larger on a slim finger and smaller on a large one. Thin bands and slim prongs make the center diamond look bigger; a halo of small diamonds adds visible size for less money than extra carats. If you can, try on settings with diamonds of the sizes you're considering before deciding.
Check a Diamond's Size and Price
Enter a GIA report number to see the diamond's exact measurements, proportions and quality checks, then unlock its estimated market price.
Check a diamond →