Carat is weight, not size. Two stones of the same carat weight can look different depending on cut and proportions. The table below gives the approximate face-up diameter of a well-cut round brilliant; other shapes at the same weight measure differently. The exact measurements of every stone we sell are on its product page, taken from its grading report.
| Carat | Approx. diameter (mm) |
|---|---|
| 0.25 | 4.1 |
| 0.50 | 5.1 |
| 0.75 | 5.8 |
| 1.00 | 6.4 |
| 1.25 | 6.9 |
| 1.50 | 7.3 |
| 2.00 | 8.1 |
| 2.50 | 8.8 |
| 3.00 | 9.3 |
| 4.00 | 10.2 |
| 5.00 | 11.0 |
A ruler against your finger is the fastest reality check: 6.4 mm is about the width of a standard pencil.