MM to Carat Weight Conversion Charts

CONVERSION CHARTS

Use these charts to look up the approximate carat weight
of your favorite gemstone by measuring the MM size

Round Gemstones

Round Faceted Gemstone Weight Chart (approximate weights)
	2mm	3mm	4mm	5mm	6mm	6.5mm	7mm	8mm	10mm
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
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

Marquise Faceted Gemstone Weight Chart (Weights are approximate)
	4x2mm	5x3mm	6x3mm	7x3.5mm	8x4mm	10x5mm	12x6mm	14x7mm
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 Cut

Octagon Faceted Gemstone Weight Chart (approximate weights)
	5x3mm	6x4mm	7x5mm	8x6mm	9x7mm	10x8mm	11x9mm	12x10mm	14x10mm
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

Oval Cut

Oval Faceted Gemstone Weight Chart (approximate weights)
	5x3mm	6x4mm	7x5mm	8x6mm	9x7mm	10x8mm	11x9mm	12x10mm	14x10mm
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 Gemstone Weight Chart (approximate weights)
	5x3mm	6x4mm	7x5mm	8x6mm	9x6mm	10x7mm	12x8mm	14x9mm
Alexandrite	.30 ct	.50 ct	.85 ct	1.10 ct	2.10 ct	3.60 ct	6.60 ct	8.80 ct
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	1.85 ct	4.20 ct	5.60 ct
Citrine	.20 ct	.35 ct	.65 ct	.85 ct	1.30 ct	1.70 ct	4.00 ct	5.00 ct
Diamond	.25 ct	.50 ct	.75 ct	1.00 ct	1.50 ct	2.00 ct	3.50 ct	5.00 ct
Emerald	.25 ct	.45 ct	.70 ct	1.05 ct	1.70 ct	2.60 ct	4.15 ct	6.10 ct
Garnet	.25 ct	.40 ct	1.00 ct	1.15 ct	1.30 ct	1.80 ct	3.50 ct	5.80 ct
Opal	.13 ct	.22 ct	.35 ct	.50 ct	.70 ct	1.03 ct	1.40 ct	2.45 ct
Peridot	.25 ct	.45 ct	.70 ct	.80 ct	1.10 ct	1.40 ct	3.40 ct	4.75 ct
Ruby	.30 ct	.50 ct	.75 ct	1.00 ct	1.85 ct	2.50 ct	4.75 ct	7.90 ct
Sapphire	.30 ct	.50 ct	.75 ct	1.00 ct	1.85 ct	2.50 ct	4.75 ct	7.90 ct
Topaz	.25 ct	.50 ct