Enter the length, width, depth, specific gravity, shape factor, and weight correction factor into the calculator to determine the gem weight.

Gem Weight Formula

The following equation is used to calculate the Gem Weight.


  • Where GW is the gem weight (carats)
  • L is the length (mm)
  • W is the width (mm)
  • D is the depth (mm)
  • SG is the specific gravity (carats/mm^3)
  • SF is the shape factor
  • WCF is the weight correction factor

What is a Gem Weight?


A Gem weight is defined as the total mass of a gemstone based on the physical characteristics of length, width, depth, specific gravity, and shape.

How to Calculate Gem Weight?

Example Problem:

The following example outlines the steps and information needed to calculate Gem Weight.

First, determine the length, width, and depth. In this example, these are 3, 4, and 2mm respectively.

Next, determine the specific gravity. The specific gravity is a measure of density, and in this case, equals 1.25 carat/mm^3.

Next, determine the shape factor and weight correction factor. These are calculated as .675 and 1.1 respectively.

Finally, calculate the gem weight using the formula above:


GW = 3*4*2*1.25*.675*1.1

GW = 22.275 carats