Glossary

Carat

Carat is the metric unit of mass for gemstones — 1 carat equals 200 milligrams (0.2 grams). For diamonds and other faceted stones, carat directly drives price; visually, it correlates with stone diameter, but two stones of equal carat can look meaningfully different depending on cut and depth.

Carat is mass, not size

A carat is a unit of weight equal to 200 milligrams. It's not a unit of size — two 1-carat stones can have visibly different diameters because density and cut depth vary by stone type and shape. A 1-carat round-brilliant diamond is ~6.5mm across the top; a 1-carat marquise diamond is roughly 10mm × 5mm. For sapphires and rubies (denser than diamond), 1 carat sits a touch smaller in face-up area than the same-mass diamond.

Why carat dominates price (for diamonds)

Diamond pricing is non-linear in carat — a 2-carat stone of the same color/clarity grade is more than 2× the price of a 1-carat. The jumps happen at psychologically round numbers (1.0, 1.5, 2.0 carats), so a 0.95-carat stone is dramatically cheaper than a 1.05-carat one despite looking nearly identical. For colored stones, carat matters less and color saturation/origin matter more.

How carat affects jewelry photography

Larger carat = bigger face-up area = easier to photograph in detail. Sub-1-carat melee stones (the tiny accent stones in a halo or pavé band) are notoriously hard to retouch because each is only a few pixels wide; AI jewelry retouching specifically guards against "simplifying" these as noise. When sellers list a stone's carat in copy, listing photos should match — a 0.5-carat ring shouldn't be photographed at extreme zoom that makes it look 2 carats.

See it in action

Pricing

Related terms

Last updated 2026-05-03