Moissanite DEW vs. Carat: What's the Difference and Why It Matters

When you shop for moissanite, you will encounter a unit of measurement called DEW — Diamond Equivalent Weight — rather than the carat weight you may be familiar with from diamond shopping. This distinction exists because moissanite and diamond are physically different materials with different densities, and a moissanite stone cut to the same physical dimensions as a diamond will weigh less than the diamond. DEW resolves this by expressing moissanite size in terms of the diamond size it visually matches — making it straightforward to find a moissanite that looks exactly the size of a 1-carat, 2-carat, or 3-carat diamond without needing to understand gemological density calculations.

Why Moissanite Uses DEW Instead of Carat

Carat is a unit of weight, not size. One carat equals 0.2 grams. When gemologists and jewelers specify a diamond by its carat weight, the carat weight provides a strong indication of the stone's physical dimensions because diamonds of a given cut style tend to have consistent proportions — a well-cut 1-carat round brilliant diamond will reliably have a diameter of approximately 6.4–6.5mm.

Moissanite is less dense than diamond. Diamond has a specific gravity of approximately 3.52; moissanite has a specific gravity of approximately 3.21. This means a moissanite stone cut to exactly the same physical dimensions as a 1-carat diamond (6.5mm diameter, round brilliant) will weigh approximately 0.88 carats on a gemological scale — not 1.00 carat. If moissanite were sold by actual carat weight, a "1-carat moissanite" would be visually smaller than a 1-carat diamond, creating confusion for buyers trying to match sizes.

DEW solves this by working backwards from physical dimensions. A moissanite described as "1.00 DEW" is cut to the same physical dimensions as a 1-carat diamond of the same shape — it will look exactly the same size as a 1-carat diamond face-up, even though its actual carat weight is approximately 0.88ct.

DEW Conversion Chart by Shape

The following dimensions represent standard DEW sizes for round brilliant moissanite:

• 0.50 DEW — 5.0mm diameter (equivalent to a 0.50ct round diamond)
• 0.75 DEW — 5.8mm diameter (equivalent to a 0.75ct round diamond)
• 1.00 DEW — 6.5mm diameter (equivalent to a 1.00ct round diamond)
• 1.50 DEW — 7.3mm diameter (equivalent to a 1.50ct round diamond)
• 2.00 DEW — 8.1mm diameter (equivalent to a 2.00ct round diamond)
• 2.50 DEW — 8.7mm diameter (equivalent to a 2.50ct round diamond)
• 3.00 DEW — 9.2mm diameter (equivalent to a 3.00ct round diamond)
• 4.00 DEW — 10.3mm diameter (equivalent to a 4.00ct round diamond)
• 5.00 DEW — 11.1mm diameter (equivalent to a 5.00ct round diamond)

For fancy shapes (oval, cushion, pear, emerald, radiant), DEW is calculated from the stone's length and width dimensions using shape-specific conversion formulas. The principle is the same: a moissanite oval described as "2.00 DEW" will have the same length and width dimensions as a 2-carat diamond oval of equivalent proportions.

What This Means When You Shop

If you know what diamond size you want to match: Simply select the same DEW number. A 2.00 DEW moissanite will look identical in size to a 2-carat diamond of the same shape when set in the same ring. Read more: Moissanite Carat Size Guide.

If you're working from physical dimensions: Use the diameter (for round) or length × width measurements (for fancy shapes) to select your DEW. Read more: Moissanite Ring Size Guide.

If you're comparing prices: Because moissanite is sold by DEW rather than actual carat weight, price-per-DEW is the correct comparison metric — not price-per-actual-carat. A 2.00 DEW moissanite at $800 costs $400 per DEW, which is the meaningful comparison to a 2-carat diamond's per-carat price. Read more: Moissanite vs. Diamond Guide.

Does DEW Affect Quality?

No. DEW is purely a size measurement system. All Moissanite Shine stones are GRA-certified DEF color (colorless) and VVS1 clarity equivalent, with Excellent cut, polish, and symmetry — regardless of their DEW size. A 0.50 DEW and a 5.00 DEW stone from Moissanite Shine carry the same quality guarantees; only their physical dimensions differ. Read more: Moissanite Color Grades Explained.

Browse moissanite rings by DEW size in our ring collection or request a custom size at our custom design service.

📐 Not sure of your size? View our Ring Size Guide & Jewelry Care Tips

Related guides:
Moissanite Carat Size Guide
Moissanite vs. Diamond Guide
Moissanite Color Grades Explained
Moissanite Clarity Grades Explained
Moissanite Certificate Guide