Utility Loft → Diamond Size → 1 Carat Size
How Big Is a 1 Carat Diamond?
A round 1 carat diamond is about 6.5 mm across — roughly a quarter inch. Because carat is a weight, the face-up size changes with shape, shown below.
Enter a carat weight above to see the diameter in millimeters.
1 carat diamond size by shape
| Shape | Face-up size at 1.00 ct |
|---|---|
| Round | 6.5 mm |
| Princess | 5.5 mm |
| Cushion | 5.6 mm |
| Oval | 7.5 × 5.5 mm |
| Emerald | 6.8 × 5.0 mm |
| Pear | 8.2 × 5.5 mm |
| Marquise | 10.0 × 5.0 mm |
Typical well-cut dimensions; elongated shapes look larger than a round of equal weight. Verify exact mm on the grading report.
Related
Frequently asked questions
How many mm is a 1 carat diamond?
A round 1 carat diamond is about 6.5 mm in diameter — roughly a quarter of an inch. Other shapes measure differently at the same weight; an oval, for example, is closer to 7.5 × 5.5 mm.
Is a 1 carat diamond big?
A 1 carat is a popular, clearly visible engagement-ring size — larger than the most common range (many rings sit between 0.5 and 1 ct) but still comfortable for everyday wear. How big it looks depends on the shape, the cut, and your finger size.
How much does a 1 carat diamond cost?
Price varies enormously with cut, color, and clarity — a 1 carat can range from around a thousand to many thousands of dollars. Size (carat) is only one of the 'four Cs', so two 1 ct stones can differ greatly in price and appearance.
Does a 1 carat look bigger on a smaller finger?
Yes — the same stone appears larger on a slimmer finger because there's less surrounding surface for comparison. If you're between finger sizes, that can make a noticeable difference; check your size with our ring size converter.