Diamond Weight (Carat) Calculator

Estimate a round-brilliant diamond's carat weight from its diameter.

How the Math Works

The Diamond Weight (Carat) Calculator uses a simplified mathematical model to estimate a round diamond's carat weight from its diameter. The formula, carat ≈ (diameter ÷ 6.5)³, assumes the diamond is a perfect sphere and relates its volume to weight. Dividing the diameter by 6.5 normalizes the measurement, and cubing the result approximates the volume, which correlates to carat weight. This formula is derived from empirical data and serves as an estimation tool, not an exact measurement, as real diamonds may vary slightly in shape and density.

Practical Applications

To use this calculator, first measure the diamond's diameter using a precise tool like a caliper or a diamond gauge. Input the diameter value into the formula by dividing it by 6.5 and then cubing the result. The final value represents the estimated carat weight. This method is particularly useful when precise scales or professional equipment are unavailable, allowing quick comparisons or preliminary assessments during gemstone shopping or appraisals.

Day-to-Day Use

This calculator aids in everyday decisions involving diamond purchases, such as comparing stones for quality or price per carat. It helps consumers gauge whether a diamond’s size aligns with its cost, ensuring better value for money. Additionally, it simplifies insurance documentation or resale preparations by providing a reliable estimate of the diamond’s weight without requiring specialized tools, making it a practical resource for both beginners and experienced jewelry enthusiasts.

Worked example

6.5 mm → ~1.0 carat.

FAQ