Convert from milimeter measurement the carat weight of round cut diamonds to know the approximate carat weight or carat weight equivelent.

Diamonds & Gemstones Conversion Charts

Convert from milimeter measurement the carat weight of round cut diamonds to know the approximate carat weight or carat weight equivelent. The weights listed below for diamonds are averages only and based on their specific gravity. Stones that have a very deep or very shallow cut or a higher or lower specific gravity will vary from these estimated carat weights.

Round Diamonds			Round Diamonds
Round Cut	Decimal Inch		Round Cut	Decimal Inch
mm width	Decimal width	Weight	mm width	Decimal width	Weight
1.0 mm	.039 inch	.005 carat	4.8 mm		.40 carat
1.2 mm		.008 carat	4.9 mm		.43 carat
1.3 mm		.01 carat	5.0 mm	.197 inch	.47 carat
1.5 mm		.015 carat	5.2 mm	.205 inch	1/2 carat
1.7 mm		.02 carat	5.4 mm		.60 carat
1.8 mm		.025 carat	5.5 mm		.63 carat
2.0 mm	.079 inch	.03 carat	5.6 mm		.65 carat
2.1 mm		.035 carat	5.8 mm	.228 inch	3/4 carat
2.2 mm		.04 carat	6.0 mm	.236 inch	.80 carat
2.4 mm		.05 carat	6.2 mm		.85 carat
2.5 mm		.06 carat	6.4 mm		.95 carat
2.7 mm		.07 carat	6.5 mm	.255 inch or 1/4 inch	1.00 carat
2.8 mm		.08 carat	6.6 mm		1.10 carat
2.9 mm		.09 carat	6.8 mm		1.17 carat
3.0 mm	.118 inch	1/10 carat	7.0 mm	.276 inch	1-1/4 carat
3.1 mm		.11 carat	7.2 mm		1.33 carat
3.2 mm	.125 inch or 1/8 inch	.12 carat	7.4 mm	.291 inch	1-1/2 carat
3.3 mm		.14 carat	7.6 mm		1.60 carat
3.4 mm		.15 carat	7.8 mm	.307 inch	1.75 carat
3.5 mm		.16 carat	8.0 mm	.315 inch	1.90 carat
3.6 mm		.17 carat	8.2 mm	323 inch	2.00 carat
3.7 mm		.18 carat	8.4 mm		2.15 carat
3.8 mm	.150 inch	1/5 carat	8.6 mm	.338 inch	2.25 carat
3.9 mm		.22 carat	8.8 mm	.346 inch	2.50 carat
4.0 mm	.158 inch	.23 carat	9.0 mm	.354 inch	2.65 carat
4.1 mm	.162 inch	1/4 carat	9.2 mm		2.85 carat
4.2 mm		.30 carat	9.4 mm	.370 inch	3.00 carat
4.4 mm	.173 inch	.33 carat	9.6 mm		3.15 carat
4.5 mm		.35 carat	9.8 mm		3.35 carat
4.6 mm	.181 inch	1/3 carat	10.0 mm	.394 inch	3-1/2 carat

Round Stones

(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