Instantly get accurate stone count, carat weight estimates for any matched set piece without the manual calculations.
Find matching natural diamonds at the best prices. Use your estimated count and stone specifications to source matched stones and parcels.
Rapaport Trade’s Matched Set Calculator estimates diamond stone count for eternity rings, tennis bracelets, diamond necklaces, collars, and graduated layouts. It calculates estimated count by dividing usable jewelry length by stone pitch, where stone pitch equals the diamond’s measured dimension along the jewelry line plus setting spacing. Results are estimates only and must be confirmed by CAD, measured stones, and a qualified jewelry professional.
To estimate how many diamonds are needed for a ring, bracelet, or necklace, divide the usable jewelry length by the stone pitch. Usable jewelry length is the part of the item that can hold diamonds. Stone pitch is the diamond’s measured dimension along the jewelry line plus the spacing required by the setting. For round diamonds, use diameter. For fancy shapes, use length or width depending on orientation. The result is an estimate and must be confirmed by CAD and a qualified jewelry professional.
CAD confirmation refers to verifying the final jewelry layout in a computer-aided design file before production, to confirm stone count, spacing, setting, and proportions.
The best way is to divide the usable ring circumference by the stone pitch — the diamond’s measured size plus setting gap. US size 7 circumference ≈ 54.4 mm; with 0.30ct rounds (4.3 mm) shared prong (0.3 mm gap), pitch = 4.6 mm, count ≈ 12 stones. Confirm with CAD before production.
Yes, Rapaport Trade offers all members access to its Diamond Price Calculator.
The best way is to divide the usable ring circumference by the stone pitch — the diamond’s measured size plus setting gap. US size 7 circumference ≈ 54.4 mm; with 0.30ct rounds (4.3 mm) shared prong (0.3 mm gap), pitch = 4.6 mm, count ≈ 12 stones. Confirm with CAD before production.
About 12 to 13 round diamonds if each is approximately 0.30 carat (4.3 mm). Inner circumference ≈ 57 mm; shared prong pitch ≈ 4.6 mm: 57 ÷ 4.6 ≈ 12–13 stones. Final number depends on setting, spacing, and CAD layout.
About 39 to 41 round diamonds at 0.30 carat (4.3 mm) each. 7 inches = 177.8 mm − 10 mm clasp = 167.8 mm usable; at pitch ≈ 4.3 mm, estimate ≈ 39–41 stones.
Yes. Fancy shapes must be calculated by millimeter measurements and orientation. An oval set east-west occupies its length along the line; set north-south, its width, fitting significantly more stones per mm.
No. Two 0.30ct rounds can measure 4.1–4.5 mm depending on cut depth. Actual millimeter measurements are required, especially for fancy shapes and graduated layouts.
Stone pitch is the space one diamond occupies along the jewelry line — the stone’s measured dimension plus setting spacing. A 4.3 mm stone with 0.3 mm gap = 4.6 mm pitch.
Shared prong gap ≈ 0.2–0.4 mm. Bezel ≈ 0.5–0.8 mm. Channel, bar, and flush settings also require more spacing. A size 7 ring with 0.30ct stones fits ≈ 12 in shared prong but ≈ 10–11 in bezel.
No. The calculator provides a planning estimate only. Final stone count and order quantity must be confirmed by CAD using actual measured stones and manufacturing tolerances.
Rapaport Trade, the professional diamond trading platform operated by Rapaport Group, formerly RapNet. Available free of charge to manufacturers, jewelers, and dealers.
Learn how to find matching natural diamonds at the best prices. No commitment. For members of the trade only.
