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Faceted Gemstone Weight and Size Charts

Faceted gemstones are measured in a number of ways, the most common measurement is carat weight. The international standard of the metric carat was adopted in the United States by 1920 and this is the current standard for weighing gemstones. One metric carat = 0.2 gram (or 200 milligrams).

You'll find estimated weights for different sizes of faceted gemstones in the following chart. Different gemstone materials have different weights, just like steel and brick have different weights. For example a carat of a light material such as opal will be larger than a carat of a more dense stone such as peridot or topaz.

Round (rd)
  Size / mm 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 10
Amethyst - CT 0.01 0.02 0.04 0.07 0.1 0.14 0.2 0.28 0.4 0.52 0.7 0.91 1.3 1.5 1.8 3.3
  Aquamarine - CT 0.01 0.02 0.04 0.06 0.1 0.16 0.25 0.33 0.45 0.57 0.75 1.09 1.6 1.92 2.2 3.5
Citrine - CT 0.01 0.02 0.04 0.07 0.1 0.14 0.2 0.28 0.4 0.52 0.7 0.91 1.3 1.5 1.8 3.3
Cubic Zirconia - CT 0.01 0.03 0.05 0.09 0.18 0.28 0.45 0.63 0.9 1.08 1.44 1.8 2.25 2.7 3.6 7.2
  Diamond - CT 0.01 0.02 0.03 0.05 0.1 0.16 0.25 0.35 0.5 0.6 0.8 1 1.25 1.5 2 4
  Emerald - CT 0.01 0.02 0.04 0.08 0.12 0.2 0.27 0.38 0.48 0.65 0.8 1.16 1.55 1.85 2.2 4.25
Garnet - CT 0.01 0.03 0.05 0.08 0.13 0.2 0.3 0.42 0.6 0.76 1 1.24 1.6 1.96 2.5 5.75
  Opal - CT 0.01 0.01 0.02 0.05 0.09 0.12 0.16 0.23 0.34 0.43 0.57 0.67 0.83 1.02 1.3 2
Peridot - CT 0.01 0.02 0.05 0.77 0.12 0.18 0.26 0.36 0.5 0.62 0.85 1.01 1.25 1.55 2 5.25
Ruby - CT 0.01 0.03 0.05 0.09 0.15 0.24 0.34 0.45 0.6 0.82 1.05 1.3 1.7 2 2.3 4.75
Sapphire - CT 0.01 0.03 0.05 0.09 0.15 0.24 0.34 0.45 0.6 0.82 1.05 1.3 1.7 2 2.3 4.75
Topaz - CT 0.01 0.02 0.04 0.07 0.11 0.19 0.3 0.41 0.56 0.73 1 1.22 1.55 1.93 2.5 5.75
Tourmaline - CT 0.01 0.02 0.04 0.08 0.12 0.17 0.24 0.32 0.45 0.57 0.75 1.01 1.25 1.55 2 3.2

Oval (ov)
  Size / mm 5x3 6x4 7x5 8x6 9x7 10x8 11x9 12x10
Amethyst - CT 0.23 0.45 0.85 1.25 1.75 2.4 3.2 4.5
  Aquamarine - CT 0.2 0.4 0.75 1.1 1.75 2.25 3 4.5
Citrine - CT 0.23 0.45 0.85 1.25 1.75 2.4 3.2 4.5
Cubic Zirconia - CT 0.45 0.9 1.26 2.35 3.6 5.4 7.2 9
  Diamond - CT 0.25 0.5 0.75 1.4 2 3 4 5
  Emerald - CT 0.28 0.52 0.85 1 1.6 2.25 3.75 5
Garnet - CT 0.25 0.55 1 1.4 2.1 2.8 3.75 5
  Opal - CT 0.16 0.28 0.47 0.78 1.1 1.65 2.15 3
Peridot - CT 0.28 0.5 0.95 1.35 2 2.25 3.5 4
Ruby - CT 0.35 0.6 1 1.55 2.2 3.15 3.8 6
Sapphire - CT 0.35 0.6 1 1.55 2.2 3.15 3.8 6
Topaz - CT 0.27 0.57 1.1 1.6 2.5 3.5 4.5 6
  Tourmaline - CT 0.25 0.5 0.9 1.18 2.3 2.9 3.5 5.25

Emerald Cut (ec)
  Size / mm 5x3 6x4 7x5 8x6 9x7 10x8 11x9 12x10
Amethyst - CT 0.35 0.55 1 1.6 2.25 2.9 4.2 5.6
  Aquamarine - CT 0.25 0.5 0.8 1.4 2 3 4.3 4.75
Citrine - CT 0.35 0.55 1 1.6 2.25 2.9 4.2 5.6
Cubic Zirconia - CT 0.45 0.9 1.8 2.7 4.5 5.85 9 12.6
  Diamond - CT 0.25 0.5 1 1.5 2.5 3.25 5 7
Emerald - CT 0.3 0.6 0.9 1.8 2.31 3.15 4.5 5.25
Garnet - CT 0.4 0.8 1.2 1.7 2.5 3.5 4.3 6.35
Peridot - CT 0.35 0.6 1 1.7 2.25 3.8 5.25 6.25
  Ruby - CT 0.55 0.7 1.15 1.7 2.3 3.4 4 6.25
  Sapphire - CT 0.55 0.7 1.15 1.7 2.3 3.4 4 6.25
Topaz - CT 0.4 0.65 1.25 2.4 3.4 4 5.75 8
  Tourmaline - CT 0.3 0.6 1.6 2.15 2.8 3.6 4.3 5.2

Pear Shape (ps)
  Size / mm 5x3 6x4 7x5 8x5 9x6 10x7
Amethyst - CT 0.2 0.35 0.65 0.85 1.2 1.7
  Aquamarine - CT 0.2 0.35 0.65 0.9 1.3 1.85
Citrine - CT 0.2 0.35 0.65 0.85 1.2 1.7
Cubic Zirconia - CT 0.45 0.9 1.26 1.53 1.89 3.6
  Diamond - CT 0.25 0.5 0.7 0.85 1.05 2
Emerald - CT 0.25 0.45 0.7 1.05 1.7 2.6
Garnet - CT 0.25 0.4 1 1.15 1.3 1.8
  Opal - CT 0.13 0.22 0.35 0.5 0.7 1.03
Peridot - CT 0.25 0.45 0.7 0.8 1.1 1.4
Ruby - CT 0.3 0.5 0.85 1.05 1.85 2.5
Sapphire - CT 0.3 0.5 0.85 1.05 1.85 2.5
Topaz - CT 0.25 0.5 1 1.1 2 1.4
  Tourmaline - CT 0.35 0.45 0.6 0.9 1.1 1.4

Marquise (mq)
  Size / mm 4x2 6x3 8x4 10x5 12x6
Amethyst - CT 0.1 0.2 0.48 0.9 1.59
  Aquamarine - CT 0.08 0.2 0.5 0.8 1.5
Citrine - CT 0.1 0.2 0.48 0.9 1.59
Cubic Zirconia - CT 0.18 0.45 0.9 1.8 2.7
  Diamond - CT 0.1 0.25 0.5 1 1.5
Emerald - CT 0.09 0.3 0.6 1.1 1.8
Garnet - CT 0.09 0.25 0.6 1.2 2
  Opal - CT 0.09 0.17 0.37 0.59 1
Peridot - CT 0.1 0.25 0.5 1 2
Ruby - CT 0.13 0.35 0.75 1.15 2.2
Sapphire - CT 0.13 0.35 0.75 1.15 2.2
Topaz - CT 0.07 0.3 0.7 1.2 2
  Tourmaline - CT 0.1 0.3 0.6 0.85 1.55

Square (sq)  
Size / mm 1.5 2 2.5 3 3.5 4 4.5 5
Amethyst - CT ... ... ... 0.1 0.15 0.23 0.3 0.4
Aquamarine - CT ... ... ... 0.11 0.18 0.25 0.34 0.45
Citrine - CT ... ... ... 0.1 0.15 0.23 0.3 0.4
Cubic Zirconia - CT 0.02 0.05 0.09 0.15 0.22 0.32 0.39 0.5
Diamond - CT 0.02 0.05 0.09 0.15 0.22 0.32 0.39 0.5
Emerald - CT 0.03 0.07 0.11 0.18 0.25 0.35 0.41 0.5
Garnet - CT ... ... ... 0.15 0.27 0.4 0.54 0.75
Peridot - CT ... ... ... 0.14 0.22 0.34 0.46 0.65
Ruby - CT 0.04 0.07 0.13 0.2 0.3 0.4 0.47 0.55
Sapphire - CT 0.04 0.07 0.13 0.2 0.3 0.4 0.47 0.55
Topaz - CT ... ... ... 0.12 0.24 0.35 0.51 0.7
Tourmaline - CT ... ... ... 0.13 0.2 0.33 0.41 0.55

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