A 0.5 carat round diamond measures about 5.11 mm across and covers roughly 20.5 mm² seen from above.
Carat is weight, not size, so the same 0.5 ct buys visibly different dimensions depending on shape. At this weight the gap between the shape that spreads widest (emerald) and the most compact (cushion) is about 24% of face-up area — for the same weight, and broadly the same price.
| Shape | Length × width (mm) | Face-up area (mm²) |
|---|---|---|
| Round | 5.11 × 5.11 | 20.5 |
| Oval | 6.28 × 4.49 | 22.1 |
| Cushion | 4.63 × 4.41 | 18.3 |
| Pear | 6.70 × 4.32 | 19.7 |
| Marquise | 7.75 × 4.08 | 22.2 |
| Emerald | 5.73 × 4.10 | 22.7 |
| Radiant | 5.08 × 4.23 | 20.7 |
| Princess | 4.35 × 4.35 | 19.0 |
| Asscher | 4.51 × 4.51 | 19.4 |
Face-up area is what the eye reads as "big". Two 0.5 ct stones can differ by a fifth in the area they cover while weighing exactly the same, because depth hides weight underneath, where nobody sees it.
A figure in millimetres is hard to picture, and photographs of other people's hands are worse than useless — the same stone on a slender finger looks like a bigger stone. This tool renders it at true millimetre scale on a photo of your hand, calibrated from your ring size or a bank card, so the size on screen is the real one. The photo is processed on your device and never uploaded.
See 0.5 ct on your own hand →