Gemstone weight calculator for set stones

An online tool for estimating the weight of set stones in a piece of jewelry from caliper measurements. It works out the stone weight in carats and grams, subtracts it from the total item weight, and shows the net metal weight. Supports diamond, cubic zirconia, corundum and dozens of other stones.

How to calculate stone weight

1
Weigh the item

Enter the gross weight in grams and pick the metal fineness — for the net-metal figure.

2
Measure the stone

With calipers, right in the setting: diameter for a round stone, length and width for the rest, and depth where you can.

3
Pick the cut and stone

Cubic zirconia sits second — it is ~1.75× heavier than a diamond of the same size. If the depth is hidden by the setting, turn on the estimate.

4
Read the result

Stone weight in carats and grams, net metal weight (gross minus stones) and its value at your rate.

Work out stone and net-metal weight from the measurements

The piece
g
The whole item on the scale, stones included.
fineness
$ / g
Your rate per gram of metal at this fineness — for the estimate. Optional.
Set stones 0
Result
Add the item weight and at least one stone — the result shows up here.
Stones weight
0 ct 0 g
Net metal weight · gross minus stones
0 g
Pure precious metal · by fineness
0 g
Metal value
0 $
Reference
Diameter → carats (round)

For a normally-cut round stone. Cubic zirconia of the same diameter is heavier.

Ø, mmDiamond, ctCubic zirconia, ct

Measure with calipers or a jeweler’s gauge across the top of the stone, without removing it from the piece.

Stone densities
StoneDensity, g/cm³

What the calculator does

Multi-stone list
Several stones in one piece: channels, pavé, solitaires. A quantity for identical stones. The total is subtracted from the gross automatically.
Cubic zirconia as its own class
A CZ preset with density 5.80: at the same size it is ~1.75× heavier than a diamond. A twin “diameter → carats” table for diamond and CZ.
13 GIA cut shapes
Round, oval, cushion, princess, emerald, marquise, pear, heart, baguette, cabochon and more. The marquise, pear and emerald coefficients adapt to the length-to-width ratio.
41 stones with accurate densities
From diamond and corundum to opal and glass; you can enter a custom density. Values from IGS and GemSelect references.
Hidden-depth estimate
If the pavilion cannot be measured, the tool estimates depth from the cut — deeper for cubic zirconia. Enter two dimensions instead of three.
Carats, grams and net metal
Carats for the jeweler, grams for the pawnshop; the net metal weight and pure precious metal by fineness right away, plus a value at your buy-back rate.

FAQ

How accurate is the estimate?

The measurement method is accurate to about ±10–15%: the real weight depends on cut quality, girdle thickness and pavilion bulge. The tool shows a range. An exact weight only comes from a scale with the stone removed.

How do I measure a stone in the setting?

With calipers or a jeweler’s gauge across the table: diameter for a round stone, length and width for the rest. Depth if the stone is open underneath; otherwise turn on “depth hidden by setting”.

Why does telling cubic zirconia apart matter?

Cubic zirconia is nearly twice as dense as gold and ~1.75× heavier than a diamond of the same size. Counting it “as a diamond” inflates the metal weight and over-values the piece — a straight loss for a buy-back desk.

What is fineness and why is it here?

Fineness is the share of pure precious metal in the alloy (585 = 58.5% gold). The tool subtracts the stones from the gross and, by fineness, works out the pure metal and its value at your rate.

How is the weight calculated?

The volume of the cut (the product of the dimensions times a shape coefficient) is multiplied by the stone density. The coefficients are calibrated on GIA diamond formulas and scale by density for colored stones and imitations.

Can I enter a custom density?

Yes — the “custom density” field overrides the preset for rare stones, synthetics or non-standard imitations.

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Who is this tool for?
💍 Jewelry & Watches
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