The Carat Size Guide
Carat is weight; what your eye sees is millimetres of spread. This guide translates one into the other so you can choose with your eyes open. All figures are approximate for well-cut stones.
Round brilliant — weight vs face-up size
| Carat | Diameter | Reads as |
|---|---|---|
| 0.50 ct | ≈ 5.1 mm | Delicate, refined |
| 0.75 ct | ≈ 5.8 mm | Noticeable presence |
| 1.00 ct | ≈ 6.4 mm | The classic benchmark |
| 1.50 ct | ≈ 7.4 mm | Confident |
| 2.00 ct | ≈ 8.1 mm | Statement |
| 3.00 ct | ≈ 9.3 mm | Unmissable |
Note the curve: doubling the weight from 1 ct to 2 ct adds under 2 mm of diameter. Weight hides in depth — which is why cut quality matters more than the number on the certificate.
Fancy shapes at 1.00 carat
| Shape | Typical 1 ct measurements |
|---|---|
| Round | 6.4 × 6.4 mm |
| Oval | ≈ 7.7 × 5.7 mm — faces up larger |
| Cushion | ≈ 5.9 × 5.9 mm — carries weight in its depth |
| Pear | ≈ 8.6 × 5.2 mm |
| Marquise | ≈ 10.4 × 5.2 mm — the largest spread of all |
| Emerald | ≈ 6.7 × 5.0 mm |
Finger size changes everything
The same stone reads differently against different hands: a 1 ct round covers noticeably more of a size-5 finger than a size-9. Slimmer bands and elongated shapes both make a centre stone look larger; wide bands do the opposite.
The "visual carat" idea
Judge spread, not weight. A shallow-leaning 0.90 ct that measures 6.3 mm gives you a "1-carat look" for less; a deep 1.10 ct can face up smaller than a fine 1.00 ct. The measurements line on the report tells the truth — we're happy to read it with you.
Seeing it in motion
Every ring on this site carries 360° footage at each carat, in each metal — the most honest size preview short of your own hand. Configure a ring and switch between 1.0, 1.5 and 2.0 ct to watch the difference.
Ready to look? Design your ring from setting to stone, or browse the bridal sets. Questions we haven't answered here? Read the FAQ or talk to us.