Carat Weight Calculator

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

How the Math Works

The Carat Weight Calculator uses a specialized formula to estimate a round diamond's weight based on its physical dimensions. The calculation employs the equation: weight = diameter squared times depth times 0.0061. This constant factor (0.0061) accounts for the typical proportions and density of gem-quality diamonds, making it a reliable approximation for round brilliants. By squaring the diameter and multiplying by the depth, the formula essentially calculates the volume of a cylinder (which approximates the diamond's shape) and then converts it to weight using the diamond's characteristic density.

Practical Applications

To use this calculator practically, first measure your round diamond's diameter across its widest point using a precise ruler or caliper, then measure from the girdle (the edge) to the bottom of the pavilion (the depth). Input these exact measurements into the calculator - ensure diameter is in millimeters for accurate results. This estimation is particularly useful when shopping for loose diamonds or evaluating diamond jewelry, allowing you to quickly compare stones or verify if a diamond's actual size matches its stated carat weight.

Day-to-Day Use

This calculator provides valuable insights in everyday diamond-related decisions. When purchasing jewelry, it helps you detect potential discrepancies between a stone's claimed carat weight and its actual physical size, protecting you from being misled by sellers. It's also useful for insurance appraisals, estate sales, or comparing diamond investments. Additionally, understanding the relationship between size and weight helps you make informed choices when setting budgets for engagement rings or other diamond accessories, ensuring you get the best possible stone for your investment.

Worked example

A 6.5 mm stone about 4 mm deep is roughly 1.0 carat.

FAQ