Carat Weight Conversion

Convert from millimeter measurement the carat weight of round cut diamonds to know the approximate carat weight or carat weight equivalent. 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 carat4.8 mm .40 carat
1.2 mm .008 carat4.9 mm .43 carat
1.3 mm .01 carat5.0 mm.197 inch.47 carat
1.5 mm .015 carat5.2 mm.205 inch1/2 carat
1.7 mm .02 carat5.4 mm .60 carat
1.8 mm .025 carat5.5 mm .63 carat
2.0 mm.079 inch.03 carat5.6 mm .65 carat
2.1 mm .035 carat5.8 mm.228 inch3/4 carat
2.2 mm .04 carat6.0 mm.236 inch.80 carat
2.4 mm .05 carat6.2 mm .85 carat
2.5 mm .06 carat6.4 mm .95 carat
2.7 mm .07 carat6.5 mm.255 inch
or 1/4 inch		1.00 carat
2.8 mm .08 carat6.6 mm 1.10 carat
2.9 mm .09 carat6.8 mm 1.17 carat
3.0 mm.118 inch1/10 carat7.0 mm.276 inch1-1/4 carat
3.1 mm .11 carat7.2 mm 1.33 carat
3.2 mm.125 inch
or 1/8 inch		.12 carat7.4 mm.291 inch1-1/2 carat
3.3 mm .14 carat7.6 mm 1.60 carat
3.4 mm .15 carat7.8 mm.307 inch1.75 carat
3.5 mm .16 carat8.0 mm.315 inch1.90 carat
3.6 mm .17 carat8.2 mm323 inch2.00 carat
3.7 mm .18 carat8.4 mm 2.15 carat
3.8 mm.150 inch1/5 carat8.6 mm.338 inch2.25 carat
3.9 mm .22 carat8.8 mm.346 inch2.50 carat
4.0 mm.158 inch.23 carat9.0 mm.354 inch2.65 carat
4.1 mm.162 inch1/4 carat9.2 mm 2.85 carat
4.2 mm .30 carat9.4 mm.370 inch3.00 carat
4.4 mm.173 inch.33 carat9.6 mm 3.15 carat
4.5 mm .35 carat9.8 mm 3.35 carat
4.6 mm.181 inch1/3 carat10.0 mm.394 inch3-1/2 carat

Round Gemstones

(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


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