Carat weight is a terrible way to inventory cushion moissanite. A cushion cut's depth, table size and faceting style—classic versus crushed-ice—change how many carats it carries inside a given footprint. Two stones both labeled "2.00 carat" can measure 6.8mm and 7.4mm corner-to-corner, and a bench that built a setting for one cannot accept the other. Wholesale buyers who switch their cushion system to millimeters stop building the wrong mount and stop taking stones back from the bench.
Why cushion spread is inconsistent
The cushion is a square-to-rectangular brilliant with rounded corners, and cutters push it in two directions. A deeper stone holds more carats in a smaller face-up footprint; a shallower, wider one spreads the same weight across a larger visible square. Add the crushed-ice faceting trend, which uses smaller, denser facets, and the weight-to-measure relationship shifts again. The number on the tag tells you mass, not the hole your setting needs. For a client shopping on finger presence, the measured footprint is what they actually see in the mirror, not the carat number.
Measure corner-to-corner
For cushion work, record the corner-to-corner measurement in millimeters—the diagonal that actually determines the seat of a bezel or a four-prong basket. When you buy parcels, request measured stones rather than carat-only specs. Build your stock bands around common mounts:
- 5.0–5.5mm: delicate pendants, petite rings, starter studs.
- 6.5–7.0mm: the mainstream engagement cushion, your reorder core.
- 7.5–8.0mm+: statement rings and cocktail pieces, lighter stock, made-to-order tail.
Within each band, keep a note of the faceting style. A crushed-ice cushion and a classic cushion of the same measured size read differently—the crushed-ice scatters light into a frosty sparkle, the classic shows broader pattern. Clients often have a preference, and mixing the two in a product line without labeling it is how you get a return.
Match halos and mounts to the measured stone
A cushion halo has to be cut to the exact outside dimension of the center. If your stock is filed by carat, you will pull a stone that does not fit the halo you have on hand. Filed by mm, you can hand the bench a center and a halo that marry on the first try. Moissanite's 9.25 Mohs hardness and 2.65 refractive index are unchanged across these sizes, so performance holds—only the footprint moves. See the faceting difference in crushed ice versus classic cushion and cross-check sizes in the carat-to-millimeter size guide.
Tag each stone on arrival
The habit that makes this system work is a physical tag. The moment a cushion stone is accepted, label it with its measured corner-to-corner mm, its color and its faceting style. A drawer of untagged cushion stones is a drawer of future bench delays. Buy the mm you actually set, tag it, and reorder the measurements that leave the bench fastest. It is also worth holding a slightly wider tolerance on halo and station settings—build the mount to a measured range rather than a single number—so small variation between parcels does not block production.
Let the mm drive the pricing story
Why crushed ice reads bigger on the hand
A crushed-ice cushion scatters light into many small flashes, which makes the face-up square look larger and livelier than a classic cushion of the same mm. Some clients love that frosty sparkle; others want the broader, more vintage pattern of a classic cut. This is why labeling faceting style matters as much as the measurement. When a client says they want "more sparkle," they usually mean crushed ice; when they say "old mine" or "vintage," they mean classic. Getting that read right avoids a return.
How to build a cushion mount library
Because cushions are bought by mm, build your mount or basket library around measured sizes rather than carat weights. Keep a few standard heads that fit your most common diagonals, and order the rest to the measured stone. That lets you say yes to a custom cushion without re-machining a mount every time. Tag each head with the mm it fits, and your bench stops guessing. The whole system—measured stones, tagged heads, labeled faceting—adds up to a cushion line that produces fewer mistakes and faster quotes. Once the bench trusts that every stone comes with a measured tag, ordering speeds up because no one has to stop and re-measure before cutting a seat.
Because clients shop cushion on face-up size, the measured millimeter is also your sales story. A well-spread 7.2mm cushion that reads larger than its carat suggests is a value message—more stone on the hand per dollar. Selling by mm lets you explain that honestly instead of leaning on a carat figure that understates the visual size. Cushion inventory is an exercise in measuring what matters. File by millimeter, tag consistently, and your setting rejects drop to near zero. The small discipline of measuring on arrival pays back many times over in saved bench hours.