Diamond Setting Calculator.

Most "diamond calculators" online are aimed at the people buying stones - retail price calculators, resale value tools, fair-price checkers. Carit's diamond setting calculator is for the people actually setting the stones. Stone spacing, eternity layouts, pavé geometry, bead counts, and total carat weight - the math a bench setter runs every day, inside the Carit app on iOS and Android.

A setter's calculator vs a buyer's calculator

When someone searches for a "diamond setting calculator" on Google, the first page is dominated by retail-facing price calculators - tools that tell a consumer what a 1.2 ct G-VS1 round is worth this week. That's useful if you're buying or selling a loose stone. It's not useful if you've got a Size 7 shank in front of you and need to know how many 1.5 mm rounds will fit around the band with correct spacing.

Carit is the second kind of tool. It exists to answer the questions a bench setter asks the metal in front of them, not the questions a consumer asks Google about a stone on an appraisal report.

The setting calculations Carit handles

1. Stone spacing around a ring (eternity)

Given the ring's inner diameter (or size) and the stone size in millimetres, how many stones fit around the band? How much gap sits between each? Carit's eternity calculator derives the inner circumference, divides by stone width plus a bead-gap allowance, and returns both the integer stone count and the exact spacing you'll have between centres.

For a Size 7 band (17.3 mm inner diameter, 54.35 mm inner circumference) set with 2.0 mm rounds and a standard 0.3 mm bead gap: (2.0 + 0.3) = 2.3 mm per stone, 54.35 / 2.3 = 23.6 stones. Round down to 23 stones, and the real gap becomes (54.35 / 23) − 2.0 = 0.36 mm - very slightly looser than the target. Full detail and the eternity tool: eternity ring calculator →

2. Pavé layout geometry

Multi-row pavé fields need row-by-row spacing, stone offset (typically 50% offset for honeycomb pattern), and bead placement. Given field dimensions and stone size, Carit outputs row-count, stones-per-row, and offset alignment. This is the piece most setters calculate by eye and then adjust during marking out - the calculator saves about ten minutes per commission and prevents the painful "I'm one short on the last row" moment.

3. Total carat weight (TCW)

Before you set 40 melee stones, you need to know the total carat weight. Carit's TCW counter lets you enter stones by shape and size (2 × 1.3 mm round, 6 × 1.5 mm princess, and so on) and tallies the total carat weight across all shapes, using the published mm-to-carat formulas for each cut. Saves adding 40 small numbers in your head and matches what the client expects to see on the spec sheet. Full documentation: carat weight calculator →

4. Stone-size reference

Every common stone size, every common cut, in a scrollable chart. Round brilliant 1.0 mm = 0.005 ct. 1.5 mm = 0.015 ct. 2.0 mm = 0.03 ct. 3.0 mm = 0.10 ct. 4.0 mm = 0.25 ct. 5.0 mm = 0.50 ct. 6.5 mm = 1.00 ct. Useful when a client says "I've got a 0.10 carat stone, what does that look like?" and you want to show them a real-size circle on your phone.

5. Bead / grain counts for channel-set work

For channel-set and bead-set bands, Carit calculates how many beads to raise based on stone count and spacing. Four beads per stone for standard bead-setting, six for micro bead-setting with very small stones, variable for rise-and-shine configurations.

The formulas behind the calculator

Circumference from diameter

C = π × D. For a ring sized in inner diameter (mm), inner circumference in millimetres equals π × diameter. A Size 7 ring (17.3 mm inner diameter) has an inner circumference of π × 17.3 = 54.35 mm.

Stones around a ring

N = C / (S + G), rounded down. Where C is inner circumference, S is stone width, G is bead gap. Real gap after rounding = (C / N) − S.

Stone weight (mm to carat)

For round brilliants: ct = diameter² × depth × 0.00604 (where depth is typically 0.60-0.62 × diameter). For well-cut proportions, most setters use the shorthand ct = diameter³ × 0.0037 as a close approximation. For fancy shapes the factor varies: princess 0.00825, oval 0.00625, cushion 0.00750, emerald 0.00565, pear 0.00615, marquise 0.00565, asscher 0.00813, radiant 0.00840, heart 0.00620, trillion 0.00570. Full table: carat weight calculator →

Why the diamond setting calculator is in the Carit app

These aren't desktop calculations. A bench setter does this math standing over a microscope or leaning over a setting peg, with gloves or lit magnification or a piece half-pinned. The tool has to be on a phone, offline, and fast.

Carit's setting calculator lives in the app because that's where it's actually used. You open it, punch in three numbers, get the answer in under five seconds, and put the phone down. No website, no sign-in, no ads, no loading spinner.

Who uses Carit as a diamond setting calculator?

Carit is used by bench diamond setters, micro-setters, pavé specialists, bench jewellers who set their own pieces, CAD designers cross-checking setting feasibility before rendering, and jewellery students learning to plan layouts. If your day includes stone spacing, bead counts, or total carat weight, the setting module is built for you.

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