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Diamond Carat Calculator

Created by Luis Hoyos
Reviewed by Komal Rafay
Last updated: Jan 18, 2024


Diamonds symbolize luxury, elegance, and timeless beauty, but when it comes to buying one, it's not just about the looks: it's also about its weight and size, and that's where the diamond carat calculator gets in.

Carat weight is one of the most important factors determining a diamond's value. With the help of this diamond carat calculator, you can quickly calculate the total carat weight of a diamond based on its dimensions and make an informed buying or selling decision.

So, let's dive into the world of diamonds and explore how to calculate diamond carats.

How to calculate the carats of a diamond?

Our tool uses the following formulas to calculate the total carat weight of the piece of diamond:

  • Asscher = Length × Width × Depth × 0.0080 × (1 + GT) × (1 + WC);
  • Baguette = Length × Width × Depth × 0.00915 × (1 + GT) × (1 + WC);
  • Cushion = Length × Width × Depth × 0.00815 × (1 + GT) × (1 + WC);
  • Emerald = Length × Width × Depth × AF × (1 + GT) × (1 + WC);
  • Heart = Length × Width × Depth × 0.0059 × (1 + GT) × (1 + WC);
  • Oval = Length × Width × Depth × 0.0062 × (1 + GT) × (1 + WC);
  • Princess = Length × Width × Depth × 0.0083 × (1 + GT) × (1 + WC);
  • Round = Diameter² × Depth × 0.0061 × (1 + GT);
  • Trillion = Length × Width × Depth × 0.0057 × (1 + GT) × (1 + WC);
  • Marquise: Length × Width × Depth × AF × (1 + GT) × (1 + WC);
  • Pear: Length × Width × Depth × AF × (1 + GT) × (1 + WC); and
  • Radiant: Length × Width × Depth × AF × (1 + GT) × (1 + WC)

💡 where:

  • GT: Girdle thickness factor;
  • WC: Weight correction factor; and
  • AF: Adjustment factor.

💡 To correctly calculate the total carat weight with the previous formulas, the length, width, depth, and diameter must be input in millimeters. For round diamonds, the depth is around 60% of the diameter.

Girdle thickness, weight correction, and adjustment factor

To know how to calculate the carats of a diamond more accurately, you must consider the following factors:

  • GT is the ratio of the girdle thickness to the diamond diameter, usually expressed as a percentage.
    • Because of the difficulty of measuring that tiny thickness, most of the time, GT is estimated visually;
    • It usually lies between 1% (0.01) and 3% (0.03) for round diamonds.
  • The weight correction factor accounts for estimation errors caused by non-regular or non-standard shapes.
  • The adjustment factor depends on the length-to-width ratio. This diamond carat calculator finds it for you automatically.

Learn more about these three factors in our diamond weight calculator article.

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FAQ

What is the weight in carat of an 8×6 mm diamond?

The weight in carats of an 8×6 mm oval diamond will be 1.071-carat, assuming a 3.6 mm depth. The exact answer will depend on the diamond depth, girdle thickness, and geometric irregularities.

How big is a 2-carat diamond?

A 2-carat round diamond has a diameter or width of 8 mm, approximately, but the exact weight will depend on the diamond diameter, depth, and girdle thickness. Find it out with our carat calculator!

Luis Hoyos
Diamond shape
Round
diamond illustration
Diameter
mm
Depth
mm
Estimated diamond weight
ct
Adjustments (optional)
Girdle thickness
%
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