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Calcimator

Carat Weight Estimator

Estimate gemstone carat weight from dimensions and specific gravity for mounted and unmounted stones.

Inputs

mm
mm
mm

Results

Estimated Weight

3.09 ct

ShapeRound Brilliant
Weight0.62 g
Weight618.4 mg
Depth %66.7%
L:W Ratio1
How to Use This Calculator
  1. Select the gem Shape: round brilliant, oval, emerald cut, pear, or marquise.
  2. Enter the Length, Width, and Depth in millimeters using calipers or a gem gauge.
  3. Enter the Specific Gravity of the gem material (e.g., diamond = 3.52, ruby = 3.99).
  4. Review the Estimated Weight in carats — useful when a scale is unavailable.
  5. Use the result to cross-reference with price-per-carat tables for value estimation.

How the result changes with Length

LengthEstimated Weight
5.452.81 ct
189.28 ct
3317.01 ct
4523.19 ct

What each input means

Length
Longest dimension of the gemstone
Width
Width of the gemstone (same as length for round)
Depth
Total depth from table to culet
Specific Gravity
Specific gravity (Diamond=3.52, Ruby=4.0, Emerald=2.72)
Shape
Cut shape of the gemstone

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Length = 6, Width = 6, Depth = 4, Specific Gravity = 3.52 = 5 input(s) provided
  2. Calculate Estimated Weight
    Estimated Weight
    3.09 = 3.09
  3. Calculate Shape
    Shape = shape.name
    Round Brilliant = Round Brilliant
  4. Calculate Weight
    Weight
    0.618 = 0.618

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