Moissanite carat and size
Moissanite is sold by size. The carat we list is diamond equivalent weight (DEW): the weight a diamond of the same size would have. Our 1 ct stone is 6.5 mm across, the size of a 1 carat round diamond. Because moissanite is about 10% lighter than diamond, the stone itself weighs about 0.88 ct.
Size chart for round moissanite
| Listed (DEW) | Diameter | Approx. actual weight |
|---|---|---|
| 0.5 ct | 5.0 mm | About 0.45 ct |
| 1 ct | 6.5 mm | About 0.88 ct |
| 2 ct | 8.0 mm | About 1.8 ct |
| 3 ct | 9.0 mm | About 2.6 to 2.7 ct |
| 5 ct | 11.0 mm | About 4.4 to 4.6 ct |
Why DEW
Carat is a unit of weight, not size: 1 carat is 0.2 grams. Moissanite (specific gravity about 3.22) is lighter than diamond (3.52), so a moissanite and a diamond of the same size do not weigh the same. What you see on a hand is the size, so moissanite sellers give the carat of a diamond that size. We say DEW so that the number is not mistaken for the stone's own weight.
Picking a size
- 0.5 ct (5 mm): small and subtle, good for stacking and petite hands.
- 1 ct (6.5 mm): the classic engagement ring size.
- 2 ct (8 mm): a clear statement; this is where the extra fire really shows.
- 3 to 5 ct (9 to 11 mm): big and bold; best on a solitaire with a sturdy setting.
Questions
Is a 1 carat moissanite really 1 carat?
It is 1 carat diamond equivalent weight: 6.5 mm across, the size of a 1 carat diamond. The stone itself weighs about 0.88 carat, because moissanite is lighter than diamond.
What size is a 2 carat moissanite?
About 8.0 mm across for a round stone.
Does a bigger moissanite look fake?
No, but it shows more rainbow fire, and very large stones are less common as diamonds, so people may look twice. Many choose 1 to 2 ct for a natural look.
More guides
- What is moissanite?
- Moissanite vs diamond
- Moissanite vs lab-grown diamond
- What a GRA certificate means
- Will moissanite pass a diamond tester?
- Moissanite and silver care
By the moissaniteit team, Olivia Star Jewelry LLC, Florida. Updated 2026-10-11.