Standard Gem Sizes Chart

Purpose: Mass produced gem settings come in standard sizes. If a gem won’t fit in a standard setting, one needs to be custom made. This involves much more labor and therefore expense. Bear this in mind when purchasing a gem, or selecting a cut for a gem. There are circumstances where the value of a stone makes it worth cutting for maximum yield, then later paying for a custom made setting. In other circumstances, the cost of a custom setting isn’t justified by the value of the gemstone.

Sizes: A gem does not need to be the precise size of the setting. A skilled metal smith can modify a setting to accommodate a wide variety of gem sizes. Any round gem can be put in a standard setting. On other shapes there are a variety of factors to be considered. As a general rule, gems under one carat can be within .1 mm of the setting size. Over one carat, a .2 mm variance can usually be accommodated and sometimes more.

Weights: The weights given are for diamonds cut to ideal proportions. Colored stones are usually cut with greater volume than diamonds, hence they will weigh more than the chart sizes. The density of the material will also affect the weight. For example a 6.5 mm round diamond, sapphire and opal, all cut in the same proportions will all weigh different. The diamond, (with a specific gravity of 3.52,) will weigh 1 carat. A sapphire, (specific gravity 4,) will weigh 1.14 carats. The opal, (specific gravity 2.15) will only weigh .61 carats. There are subtle variations to this list. For example, some list a .25 carat diamond as measuring 4.1 mm. The point is not to take these figures too literally, but to use them as a starting point for estimating weights.

GEMSTONE SIZE CHART

Rounds Standard Gem Sizes Chart Squares Standard Gem Sizes Chart Ovals Standard Gem Sizes Chart
Size Weight Size Weight Size Weight
1.6 mm .02 carat 5 mm .75 carat 5 x 3 mm .25 carat
2 mm .03 carat 6 mm 1.3 carat 6 x 4 mm .5 carat
2.5 mm .06 carat 7 mm 2.05 carat 7 x 5 mm 1.0 carat
3 mm .10 carat 8 mm 2.9 carat 8 x 6 mm 1.5 carat
3.5 mm .16 carat 9 mm 4.4 carat 9 x 7 mm 2.5 carat
4 mm .25 carat 10 mm 6.0 carat 10 x 8 mm 3.0 carat
4.5 mm .33 carat 11 mm 8.0 carat 11 x 9 mm 4.0 carat
5 mm .50 carat 12 mm 10.35 carat 12 x 10 mm 5.0 carat
5.5 mm .65 carat 13 mm 13.2 carat 14 x 10 mm 6.0 carat
6 mm .75 carat 14 mm 16.5 carat 14 x 12 mm 8.0 carat
6.5 mm 1.0 carat 15 mm 20.25 carat 16 x 12 mm 10.5 carat
7 mm 1.25 carat 16 mm 24.6 carat 18 x 13 mm 14.2 carat
8 mm 2.0 carat 20 x 15 mm 20.3 carat
9 mm 2.75 carat 22 x 15 mm 23.5 carat
10 mm 3.5 carat 23 x 17 mm 32.2 carat
11 mm 4.6 carat 25 x 18 mm 43.0 carat
12 mm 6.0 carat 27 x 20 mm 58.5 carat
13 mm 7.75 carat 30 x 22 mm 79.6 carat
14 mm 9.65 carat
15 mm 11.85 carat
16 mm 14.35 carat
17 mm 17.25 carat
18 mm 20.5 carat
19 mm 24.0 carat
20 mm 28.0 carat
21 mm 34.8 carat
22 mm 41.8 carat
23 mm 49.8 carat
24 mm 57.9 carat
25 mm 68.7 carat
Emerald Standard Gem Sizes Chart Pear Standard Gem Sizes Chart Marquis Standard Gem Sizes Chart
6 x 4 mm .5 carat 6 x 5 mm .7 carat 4 x 2 mm .10 carat
7 x 5 mm 1.0 carat 7 x 5 mm .75 carat 5 x 2.5 mm .25 carat
8 x 6 mm 1.5 carat 8 x 5 mm 1.0 carat 6 x 3 mm .30 carat
9 x 7 mm 2.5 carat 9 x 6 mm 1.5 carat 8 x 4 mm .75 carat
10 x 8 mm 3.0 carat 10 x 7 mm 2.0 carat 10 x 5 mm 1.0 carat
11 x 9 mm 4.0 carat 11 x 7 mm 2.25 carat 12 x 6 mm 2.0 carat
12 x 10 mm 5.0 carat 12 x 8 mm 3.0 carat 14 x 7 mm 3.0 carat
14 x 10 mm 6.0 carat 13 x 9 mm 3.5 carat 16 x 8 mm 4.0 carat
14 x 12 mm 8.0 carat 15 x 10 mm 5.5 carat 18 x 9 mm 6.0 carat
16 x 12 mm 10.5 carat 16 x 12 mm 8.6 carat 20 x 10 mm 8.5 carat
18 x 13 mm 14.2 carat 18 x 13 mm 12 carat
20 x 15 mm 20.3 carat 20 x 15 mm 17.3 carat
25 x 18 mm 52.2 carat 22 x 15 mm 18.7 carat
25 x 18 mm 30.6 carat
30 x 22 mm 54.5 carat

STANDARD GEM SIZES

Compliments of The International Gem Society

See related articles by category: Reference Charts, Reference Library

Products and Services Directory

Looking for gemology related products and services? Visit our Products and Services Directory.

Scholarships

IGS seeks to encourage the advancement of students pursuing a higher education. Learn more about the 2014 Clark Scholarship.

eNews Signup

Membership Login