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 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
Diamond.jpg Round
 Cut
Decimal
Inch
Diamond.jpg

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)

TOPAZ_GEN_24171_G_rd_20lond_20blue.jpg

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