Enter the diameter in millimeters and the specific gravity into the calculator to determine the carat weight. This calculator can also evaluate any of the variables given the others are known.

Mm To Carat Conversion Formula

The following formula is used to calculate the conversion from millimeters to carats for gemstones.

C = (D^3) * SG / 0.0061


  • C is the carat weight D is the diameter in millimeters (mm) SG is the specific gravity of the gemstone (dimensionless) 0.0061 is the conversion factor from cubic millimeters to carats

To calculate the carat weight, cube the diameter in millimeters, then multiply the result by the specific gravity of the gemstone. Divide the result by the conversion factor 0.0061.

What is a Mm To Carat Conversion?

A millimeter (mm) to carat conversion is a process used to convert the size of a gemstone or pearl from millimeters to carats. This conversion is important in the jewelry industry as carats are commonly used to denote the size of these precious stones. The conversion involves using a specific formula or conversion factor, which takes into account the shape and specific gravity of the gemstone. For example, the conversion for a round diamond is different from that of an emerald cut diamond.

How to Calculate Mm To Carat Conversion?

The following steps outline how to calculate the Mm To Carat Conversion using the formula: C = (D^3) * SG / 0.0061

  1. First, determine the diameter in millimeters (D).
  2. Next, determine the specific gravity of the gemstone (SG).
  3. Next, substitute the values of D and SG into the formula: C = (D^3) * SG / 0.0061
  4. Finally, calculate the carat weight (C).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

diameter in millimeters (D) = 5

specific gravity of the gemstone (SG) = 3.5