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.
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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 |
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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 |
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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 |
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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 |
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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 |
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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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