Gemstone Metric/Inch Conversion Chart

The international standard for measuring gemstones is millimeters. If you're not familiar with the metric system, this conversion chart will help you understand gemstone sizes.
 
 
Metric SizeDecimal InchFractional Inch
1 mm.039 inch 
 .0625 inch1/16
2 mm.079 inch 
3 mm.118 inch 
 .125 inch1/8
4 mm.158 inch 
 .188 inch3/16
5 mm.197 inch 
6 mm.236 inch 
 .250 inch1/4
6.5 mm.255 inch 
7 mm.276 inch 
 .313 inch5/16
8 mm.315 inch 
9 mm.354 inch 
 .375 inch3/8
10 mm.394 inch 
11 mm.433 inch 
 .438 inch7/16
12 mm.472 inch 
 .500 inch1/2
13 mm.512 inch 
14 mm.551 inch 
 .563 inch9/16
15 mm.591 inch 
 .625 inch5/8
16 mm.630 inch 
17 mm.669 inch 
 .688 inch11/16
18 mm.709 inch 
19 mm.748 inch 
 .750 inch3/4
20 mm.787 inch 
 .813 inch13/16
21 mm.827 inch 
22 mm.866 inch 
 .875 inch7/8
23 mm.906 inch 
 .938 inch15/16
24 mm.945 inch 
25 mm.984 inch 
25.4 mm1.00 inch1
 
 
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