Diamond Sieve Size Chart

How diamond sieves work

Melee, the small diamonds set in pavé, halos and bands, come in thousands, so nobody measures them one by one. Dealers sort them with a stack of numbered plates drilled with round holes of a fixed size, from 0.80 mm (plate 0000) to 4.50 mm (plate 20). The holes step up by 0.1 mm to plate 0, by 0.05 mm from plate 1 to 5.5, and by 0.1 mm from plate 6 to 20.

A sieve size names two plates: the one the stone stays on and the one it falls through. +6.5 -7 means the stone stayed on plate 6.5 (1.80 mm holes) and passed plate 7 (1.90 mm holes), so it is 1.80–1.90 mm across. The weight per stone in the chart is an average for well-cut round brilliants.

Sieve groups traders use

The names follow common Indian trade use. Some dealers draw the edges a sieve or two either way, so check what yours means by melee or +11.

Worked example

A ring design needs 24 stones of +6.5 -7. At about 0.025 ct a stone that is 24 × 0.025 = 0.60 ct. The other way round, a 5 ct parcel of +6.5 -7 holds about 5 × 40 = 200 stones. Weigh the parcel and count a sample to check your supplier's goods against the chart.

Common mistakes

• Assuming every chart matches. Published charts differ by 10 to 20% on weight, so agree the millimetre range and the parcel weight in writing.
• Mixing up plus and minus. The plus number is the plate the stones stay on, the minus number the plate they pass. +6 -6.5 is smaller than +6.5 -7.
• Sieving fancy shapes. Sieves are for rounds. Fancy shapes pass the holes differently and are sold by millimetre size.
• Rounding the weight per stone. 0.025 ct against 0.03 ct is a 20% difference across a whole parcel.

When it's worth software

A chart answers one question. Keeping sieve-wise parcels, mixes, memo issues and returns straight across a busy office is where registers fall behind. Our diamond inventory software keeps sieve-wise parcels, memo stock and certificates in one live system. For a single stone, use the diamond mm to carat calculator.

Sources

• Leo Shine, melee diamond sizing charts, New York, updated 1 January 2023.
• Casa Jewels, diamond sieve size chart, Bangkok: weights, and the note that charts differ by 10 to 20%.
• DU Gemology, diamond sieve chart, Delhi: weights and Indian trade group names.
• GIA, "Melee: Building Blocks of Contemporary Design", 11 October 2017: size ranges vary between countries and parts of the trade.
• Stuller, mm to carat chart, May 2025, and Walt's Jewelers' size chart, to cross-check single sizes.