Carat Weight Calculator

How Diamond Carat Weight Is Estimated

Jewelers weigh finished stones on a scale, but before cutting you can estimate carat weight from millimeter measurements. Each diamond shape uses a different volume factor based on typical proportions.

Common Estimation Formulas

Round brilliant:

$$\text{carats} = \text{diameter}^2 \times \text{depth} \times 0.0061 \times (1 + \text{girdle factor})$$

Fancy shapes:

$$\text{carats} = \text{length} \times \text{width} \times \text{depth} \times \text{shape factor} \times (1 + \text{girdle factor})$$

One carat equals 0.2 grams. Results are estimates only; deep or shallow cuts, thick girdles, and irregular symmetry can shift real weight by several percent.

Frequently Asked Questions

How many grams is one carat?

One carat is exactly 0.2 grams. Multiply carats by 0.2 to convert to grams.

What size is a 1 carat round diamond?

A well-cut 1 carat round is often near 6.4 to 6.5 mm diameter with about 60% depth ratio.

Why does shape change the formula?

Different cuts pack volume differently. Princess and radiant stones use higher factors than marquise or heart shapes.

What is girdle thickness correction?

The girdle is the outer edge of the stone. Thicker girdles add measurable weight beyond the face-up dimensions.

Is this result exact?

No. It is an industry estimate from dimensions. For buying or appraisal, always weigh the stone on a calibrated scale.

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How Diamond Carat Weight Is Estimated

Common Estimation Formulas

Frequently Asked Questions

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