Free Tool
Diamond Carat to MM Chart
How big is a 1 carat diamond? It depends on the shape. This chart shows approximate face-up dimensions for every popular diamond shape at common carat weights.
Asscher
L:W 1.0:1 to 1.05:1 (square is essential for the classic Asscher look)| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 3.3 x 3.3 |
| 0.5 ct | 4.3 x 4.3 |
| 0.75 ct | 5.0 x 5.0 |
| 1 ct | 5.6 x 5.6 |
| 1.25 ct | 6.0 x 6.0 |
| 1.5 ct | 6.4 x 6.4 |
| 2 ct | 7.1 x 7.1 |
| 3 ct | 8.0 x 8.0 |
| 4 ct | 8.8 x 8.8 |
| 5 ct | 9.4 x 9.4 |
Cushion
L:W 1.0:1 to 1.10:1 (square cushion) or 1.15:1 to 1.30:1 (elongated cushion)| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 3.5 x 3.5 |
| 0.5 ct | 4.5 x 4.5 |
| 0.75 ct | 5.2 x 5.2 |
| 1 ct | 5.8 x 5.8 |
| 1.25 ct | 6.2 x 6.2 |
| 1.5 ct | 6.7 x 6.7 |
| 2 ct | 7.3 x 7.3 |
| 3 ct | 8.2 x 8.2 |
| 4 ct | 9.0 x 9.0 |
| 5 ct | 9.8 x 9.8 |
Emerald Cut
L:W 1.30:1 to 1.60:1 (classic), with 1.40-1.50:1 most desirable| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 4.5 x 3.0 |
| 0.5 ct | 5.5 x 4.0 |
| 0.75 ct | 6.2 x 4.5 |
| 1 ct | 6.9 x 5.0 |
| 1.25 ct | 7.3 x 5.3 |
| 1.5 ct | 7.8 x 5.6 |
| 2 ct | 8.5 x 6.2 |
| 3 ct | 9.8 x 7.0 |
| 4 ct | 10.8 x 7.8 |
| 5 ct | 11.6 x 8.4 |
Heart
L:W 0.90:1 to 1.10:1 (near-square proportions), with 1.00:1 most desirable| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 3.8 x 3.8 |
| 0.5 ct | 5.0 x 5.0 |
| 0.75 ct | 5.8 x 5.8 |
| 1 ct | 6.5 x 6.5 |
| 1.25 ct | 6.9 x 6.9 |
| 1.5 ct | 7.4 x 7.4 |
| 2 ct | 8.1 x 8.1 |
| 3 ct | 9.2 x 9.2 |
| 4 ct | 10.0 x 10.0 |
| 5 ct | 10.8 x 10.8 |
Marquise
L:W 1.75:1 to 2.25:1 (classic), with 1.85-2.10:1 most desirable| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 5.5 x 2.8 |
| 0.5 ct | 7.5 x 3.8 |
| 0.75 ct | 8.5 x 4.5 |
| 1 ct | 10.0 x 5.0 |
| 1.25 ct | 10.5 x 5.5 |
| 1.5 ct | 11.5 x 5.8 |
| 2 ct | 12.5 x 6.3 |
| 3 ct | 14.0 x 7.0 |
| 4 ct | 15.0 x 7.5 |
| 5 ct | 16.0 x 8.0 |
Oval
L:W 1.30:1 to 1.50:1 (classic oval), with 1.35-1.45:1 most popular| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 5.0 x 3.5 |
| 0.5 ct | 6.0 x 4.0 |
| 0.75 ct | 7.0 x 5.0 |
| 1 ct | 7.7 x 5.7 |
| 1.25 ct | 8.0 x 6.0 |
| 1.5 ct | 8.5 x 6.5 |
| 2 ct | 9.5 x 7.0 |
| 3 ct | 11.0 x 7.5 |
| 4 ct | 12.0 x 8.5 |
| 5 ct | 13.0 x 9.0 |
Pear
L:W 1.45:1 to 1.75:1 (classic teardrop), with 1.50-1.65:1 most popular| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 5.0 x 3.3 |
| 0.5 ct | 6.5 x 4.3 |
| 0.75 ct | 7.5 x 5.0 |
| 1 ct | 8.0 x 5.5 |
| 1.25 ct | 8.5 x 5.8 |
| 1.5 ct | 9.0 x 6.0 |
| 2 ct | 10.0 x 6.7 |
| 3 ct | 11.5 x 7.5 |
| 4 ct | 12.5 x 8.3 |
| 5 ct | 13.5 x 9.0 |
Princess
L:W 1.0:1 to 1.05:1 (square, most popular) or 1.05:1 to 1.20:1 (slightly rectangular)| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 3.3 x 3.3 |
| 0.5 ct | 4.2 x 4.2 |
| 0.75 ct | 4.9 x 4.9 |
| 1 ct | 5.5 x 5.5 |
| 1.25 ct | 5.9 x 5.9 |
| 1.5 ct | 6.3 x 6.3 |
| 2 ct | 7.0 x 7.0 |
| 3 ct | 7.9 x 7.9 |
| 4 ct | 8.7 x 8.7 |
| 5 ct | 9.3 x 9.3 |
Radiant
L:W 1.0:1 to 1.05:1 (square) or 1.15:1 to 1.40:1 (rectangular)| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 3.5 x 3.5 |
| 0.5 ct | 4.5 x 4.5 |
| 0.75 ct | 5.2 x 5.2 |
| 1 ct | 5.7 x 5.7 |
| 1.25 ct | 6.1 x 6.1 |
| 1.5 ct | 6.5 x 6.5 |
| 2 ct | 7.2 x 7.2 |
| 3 ct | 8.1 x 8.1 |
| 4 ct | 8.9 x 8.9 |
| 5 ct | 9.5 x 9.5 |
Round Brilliant
L:W 1.0:1 (perfect circle)| Carat | Approximate Size (mm) |
|---|---|
| 0.25 ct | 4.1 |
| 0.5 ct | 5.1 |
| 0.75 ct | 5.8 |
| 1 ct | 6.5 |
| 1.25 ct | 6.9 |
| 1.5 ct | 7.4 |
| 2 ct | 8.2 |
| 3 ct | 9.3 |
| 4 ct | 10.2 |
| 5 ct | 11.0 |
About These Measurements
These are approximate face-up dimensions for well-cut stones. Actual size varies depending on cut depth and proportions. A shallow-cut stone appears larger face-up but sacrifices brilliance. A deep-cut stone looks smaller but may have better light return.
For round diamonds, the measurement is diameter. For fancy shapes, it's length x width. The measurements assume ideal or near-ideal proportions as defined by GIA excellent-cut parameters.
When shopping, always request the actual mm measurements from the grading report rather than relying on carat weight alone.