AJS Gemstone Weight Chart

These charts show the relationship between size and weight for different gemstone varieties in various shapes. Since gem varieties vary in density, two 1 carat gemstones may show a significant difference in size.
 
Round Faceted
2 mm 3 mm 4 mm 5 mm 6 mm 6.5 mm 7 mm 8 mm 10 mm
Alexandrite .04 ct .12 ct .35 ct .63 ct 1.30 ct 1.86 ct 2.15 ct 2.90 ct 5.20 ct
Amethyst .04 ct .10 ct .20 ct .40 ct .70 ct 1.10 ct 1.30 ct 1.80 ct 3.30 ct
Aquamarine .04 ct .10 ct .25 ct .45 ct .75 ct 1.31 ct 1.60 ct 2.40 ct 3.50 ct
Citrine .04 ct .10 ct .20 ct .40 ct .70 ct 1.10 ct 1.30 ct 1.80 ct 3.30 ct
Diamond .03 ct .10 ct .23 ct .47 ct .80 ct 1.00 ct 1.25 ct 1.90 ct 3.50 ct
Emerald .04 ct .12 ct .27 ct .48 ct .80 ct 1.26 ct 1.70 ct 2.50 ct 6.10 ct
Garnet .05 ct .13 ct .30 ct .60 ct 1.00 ct 1.40 ct 1.60 ct 2.50 ct 5.75 ct
Opal .02 ct .09 ct .16 ct .34 ct .57 ct .75 ct .83 ct 1.30 ct 2.00 ct
Peridot .05 ct .12 ct .26 ct .50 ct .85 ct 1.11 ct 1.25 ct 2.00 ct 5.25 ct
Ruby .05 ct .15 ct .34 ct .65 ct 1.05 ct 1.41 ct 1.60 ct 2.25 ct 4.50 ct
Sapphire .05 ct .15 ct .34 ct .65 ct 1.05 ct 1.41 ct 1.60 ct 2.25 ct 4.50 ct
Topaz .04 ct .11 ct .30 ct .56 ct 1.00 ct 1.36 ct 1.55 ct 2.50 ct 5.75 ct
Tourmaline .04 ct .12 ct .24 ct .45 ct .75 ct 1.28 ct 1.55 ct 2.00 ct 3.00 ct
Zircon .06 ct .17 ct .36 ct .69 ct 1.25 ct 1.58 ct 1.75 ct 2.60 ct 5.00 ct
 
Oval Faceted
5x3 mm 6x4 mm 7x5 mm 8x6 mm 9x7 mm 10x8 mm 11x9 mm 12x10 mm 14x10 mm
Alexandrite .30 ct .51 ct .80 ct 1.45 ct 2.00 ct 3.60 ct 4.25 ct 6.00 ct 8.90 ct
Amethyst .23 ct .45 ct .85 ct 1.25 ct 1.75 ct 2.40 ct 3.20 ct 4.50 ct 6.50 ct
Aquamarine .20 ct .40 ct .75 ct 1.10 ct 1.75 ct 2.25 ct 3.00 ct 4.50 ct 6.75 ct
Citrine .23 ct .45 ct .85 ct 1.25 ct 1.75 ct 2.40 ct 3.25 ct 4.20 ct 5.20 ct
Diamond .25 ct .50 ct .75 ct 1.40 ct 2.00 ct 3.00 ct 4.00 ct 5.00 ct 8.00 ct
Emerald .25 ct .52 ct .85 ct 1.26 ct 1.90 ct 2.60 ct 3.75 ct 5.00 ct 7.50 ct
Garnet,
Mozambique		 .25 ct .55 ct 1.00 ct 1.40 ct 2.10 ct 2.80 ct 3.75 ct 5.00 ct 7.00 ct
Garnet,
Rhodolite		 .25 ct .55 ct 1.00 ct 1.40 ct 2.10 ct 2.80 ct - - -
Iolite .21 ct .40 ct .63 ct 1.02 ct - - - - -
Opal .16 ct .28 ct .47 ct .78 ct 1.10 ct 1.65 ct 2.15 ct 3.00 ct 4.00 ct
Peridot .28 ct .50 ct .95 ct 1.35 ct 2.00 ct 2.50 ct 3.50 ct 4.00 ct 6.00 ct
Ruby .35 ct .60 ct 1.06 ct 1.55 ct 2.20 ct 3.15 ct 3.80 ct 6.00 ct 7.25 ct
Sapphire .35 ct .60 ct 1.00 ct 1.55 ct 2.20 ct 3.15 ct 3.80 ct 6.00 ct 7.25 ct
Tanzanite .20 ct .48 ct .89 ct 1.35 ct - - - - -
Topaz .28 ct .57 ct 1.10 ct 1.60 ct 2.50 ct 3.50 ct 4.50 ct 6.00 ct 8.80 ct
Tourmaline .25 ct .50 ct .90 ct 1.18 ct 2.30 ct 2.90 ct 3.50 ct 5.25 ct 6.80 ct
Tsavorite .28 ct .52 ct .75 ct - - - - - -
Zircon .40 ct .75 ct 1.45 ct 2.00 ct 2.85 ct 4.00 ct 5.60 ct 7.50 ct 8.20 ct
 
Pear Faceted
5x3 mm 6x4 mm 7x5 mm 8x6 mm 9x6 mm 10x7 mm 12x8 mm 14x9 mm
 Alexandrite .30 ct .50 ct .85 ct 1.10 ct 2.10 ct 3.60 ct 6.60ct 8.80ct
Amethyst .20 ct .35 ct .65 ct .85 ct 1.25 ct 1.70 ct 4.00 ct 5.00 ct
Aquamarine .20 ct .35 ct .65 ct .90 ct 1.30 ct 1.85ct 4.20ct 5.60ct
Citrine .20 ct .35 ct .65 ct .85 ct 1.30 ct 1.70 ct 4.00ct 5.00ct
Diamond .25 ct .50 ct .75 ct 1.00 ct 1.50 ct 2.00 ct 3.50 ct 5.00ct
Emerald .25 ct .45 ct .70 ct 1.05 ct 1.70ct 2.60ct 4.15ct 6.10ct
Garnet .25 ct .40 ct 1.00 ct 1.15 ct 1.30 ct 1.80ct 3.50ct 5.80ct
Opal .13 ct .22 ct .35 ct .50 ct .70 ct 1.03 ct 1.40ct 2.45ct
Peridot .25 ct .45 ct .70 ct .80 ct 1.10 ct 1.40 ct 3.40ct 4.75ct
Ruby .30 ct .50 ct .75 ct 1.00 ct 1.85 ct 2.50ct 4.75ct 7.90ct
Sapphire .30 ct .50 ct .75 ct 1.00 ct 1.85 ct 2.50ct 4.75ct 7.90ct
Topaz .25 ct .50 ct 1.00 ct 1.10 ct 2.00 ct 3.50 ct 6.50ct 8.50ct
Tourmaline .35 ct .45 ct .60 ct .90 ct 1.10 ct 1.40 ct 2.80 ct 6.75ct
Zircon .30 ct .70 ct 1.00 ct 1.30 ct 2.60 ct 4.00 ct 5.25 ct 7.50ct
 
Marquise Faceted
4x2 mm 5x3 mm 6x3 mm 7x3.5 mm 8x 4mm 10x5 mm 12x6 mm 14x7 mm
Alexandrite .07 ct .20 ct .30 ct .50 ct .70 ct 1.25 ct 2.10 ct 3.50 ct
Amethyst .10 ct .15 ct .20 ct .34 ct .48 ct .90 ct 1.59 ct 2.45 ct
Aquamarine .08 ct .14 ct .20 ct .25 ct .50 ct .80 ct 1.50 ct 2.75 ct
Citrine .10 ct .15 ct .20 ct .35 ct .50 ct .90 ct 1.59 ct 2.45 ct
Diamond .12 ct .18 ct .25 ct .37 ct .50 ct 1.00 ct 2.00 ct 3.00 ct
Emerald .09 ct .19 ct .30 ct .45 ct .60 ct 1.40 ct 1.80 ct 2.80 ct
Garnet .09 ct .16 ct .25 ct .42 ct .60 ct 1.20 ct 2.00 ct 2.85 ct
Opal .09 ct .13 ct .17 ct .27 ct .37 ct .59 ct 1.00 ct 1.25 ct
Peridot .10 ct .17 ct .25 ct .37 ct .50 ct 1.00 ct 2.00 ct 2.55 ct
Ruby .13 ct .24 ct .35 ct .55 ct .75 ct 1.15 ct 2.20 ct 3.00 ct
Sapphire .13 ct .24 ct .35 ct .55 ct .75 ct 1.15 ct 2.20 ct 3.00 ct
Topaz .07 ct .17 ct .30 ct .50 ct .70 ct 1.20 ct 2.00 ct 3.40 ct
Tourmaline .10 ct .20 ct .30 ct .45 ct .60 ct .85 ct 1.55 ct 2.20 ct
Zircon .13 ct .23 ct .33 ct .55 ct .75 ct 1.25 ct 1.95 ct 3.00 ct
 
Octagon Faceted
5x3 mm 6x4 mm 7x5 mm 8x6 mm 9x7 mm 10x8 mm 11x9 mm 12x10 mm 14x10 mm
Alexandrite .40 ct .70 ct 1.30 ct 2.60 ct 3.60 ct 4.20 ct 6.00 ct 8.50 ct 9.90 ct
Amethyst .35 ct .55 ct 1.00 ct 1.60 ct 2.25 ct 2.90 ct 4.20 ct 5.60 ct 7.25 ct
Aquamarine .25 ct .50 ct .80 ct 1.40 ct 2.00 ct 3.00 ct 4.30 ct 4.75 ct 7.75 ct
Citrine .35 ct .55 ct 1.00 ct 1.60 ct 2.25 ct 2.90 ct 4.20 ct 5.60 ct 7.25 ct
Diamond .25 ct .50 ct 1.00 ct 1.50 ct 3.00 ct 4.00 ct 5.00 ct 7.80 ct 8.80 ct
Emerald .30 ct .60 ct .90 ct 1.80 ct 2.31 ct 3.15 ct 4.50 ct 5.25 ct 5.80 ct
Garnet .40 ct .80 ct 1.20 ct 1.70 ct 2.50 ct 3.50 ct 4.30 ct 6.35 ct 9.00 ct
Peridot .35 ct .60 ct 1.00 ct 1.70 ct 2.25 ct 3.80 ct 5.25 ct 6.25 ct 8.80 ct
Ruby .55 ct .75 ct 1.15 ct 1.60 ct 2.30 ct 2.75 ct 4.00 ct 6.25 ct 9.00 ct
Sapphire .55 ct .75 ct 1.15 ct 1.75 ct 2.30 ct 2.75 ct 4.00 ct 6.25 ct 9.00 ct
Topaz .40 ct .65 ct 1.25 ct 2.40 ct 3.40 ct 4.00 ct 5.75 ct 8.00 ct 9.50 ct
Tourmaline .30 ct .60 ct 1.60 ct 2.15 ct 2.80 ct 3.60 ct 4.30 ct 5.20 ct 8.50 ct
Zircon .60 ct .85 ct 1.70 ct 2.35 ct 3.90 ct 4.50 ct 6.20 ct 7.01 ct 8.95 ct