Our Online Gifts and Gadgets Galore

STANDARD GEM SIZES

Compliments of
The International Gem Society

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		Squares		Ovals
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

"MOH'S SCALE OF HARDNESS"

Compliments of
The International Gem Society

Emerald		Pear		Marquis
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

"LAP MATERIALS"

Compliments of
The International Gem Society