Diamond Size Chart: Lab Grown Diamond Carat to MM

A 1 carat round diamond measures about 6.4 mm across. Other 1 carat shapes measure roughly: oval 7.7 x 5.7 mm, cushion 6.0 mm, emerald 7.0 x 5.0 mm, pear 8.0 x 5.5 mm, princess 5.5 mm and marquise 10.0 x 5.0 mm.

A 2 carat round diamond is about 8.1 mm across, and a 2 carat oval is about 9.7 x 7.2 mm. Diameter grows more slowly than weight, so doubling the carat weight does not double the size.

A 3 carat round diamond is about 9.3 mm across. A 3 carat oval is about 11.1 x 8.2 mm and a 3 carat emerald cut is about 9.8 x 7.2 mm.

In The Knot's 2026 Real Weddings Study of more than 10,000 US couples married in 2025, the average engagement ring center stone was about 2 carats, and round (26%) and oval (25%) were the most chosen shapes. A 2 carat round diamond is about 8.1 mm across and a 2 carat oval is about 9.7 x 7.2 mm. Browse our 2 carat lab grown diamond rings to see the size in real settings.

Jewelers most often recommend 1 carat total weight for everyday diamond studs: two 0.5 carat diamonds of about 5.1 mm each. A 0.5 carat total weight pair (two 0.25 carat stones of about 4.0 mm) gives a subtle look, and 1.5 to 2 carat total weight pairs (about 5.8 to 6.4 mm per stone) make a bolder statement.

Most solitaire diamond pendants are between 0.25 and 1 carat. For everyday wear, 0.5 to 1 carat is the most common range, about 5.1 to 6.4 mm for a round diamond; pendants of 1 carat and above are usually chosen as statement pieces.

Yes. Lab grown diamonds have the same chemical composition and density as mined diamonds, so a lab grown diamond of a given carat weight and cut has the same dimensions as a natural one.

Carat measures weight, not size: 1 carat equals 0.2 grams. Two diamonds of the same carat weight can look different in size because of their shape and cut proportions.

Elongated shapes such as marquise, oval and pear spread their weight across a longer outline, so they generally look larger face-up than a round, princess or asscher diamond of the same carat weight.

Stud earrings are sold by total carat weight for the pair. A 1 carat total weight pair has two 0.5 carat diamonds of about 5.1 mm each; a 2 carat total weight pair has two 1 carat diamonds of about 6.4 mm each.

The sizes are typical measurements for well-cut diamonds. Each diamond's exact dimensions vary slightly with its cut proportions, so check the measurements on the diamond's grading report before you buy.

Use the diamond size on hand simulator above: choose your ring size, shape and carat weight to see the stone drawn to scale on a finger of that size.

Grown Leo offers IGI certified loose lab grown diamonds from 1 to 10 carats in 10 shapes: round, oval, cushion, emerald, pear, radiant, princess, marquise, asscher and heart.