Jewellery specification & sizing

To help you, we have put together a small chart of more common sizes in millimetres and their gauge, and factional inch conversion    

1.5mm - 14g
2.0mm - 12g
2.5mm - 10g
3.0mm - 8g
3.5mm
4.0mm - 6g
4.5mm
5.0mm - 4g
5.5mm
6.0mm
6.5mm - 2g
7.0mm - 1g
7.5mm  
8.0mm - 0g
8.5mm
9.0mm - 00g
9.5mm - 3/8”
10mm
11mm - 7/16”
12mm
13mm - 1/2”
14mm - 9/16”
15mm
16mm - 5/8”
17mm
18mm - 11/16”
19mm - 3/4”
20mm
21mm - 13/16”
22mm - 7/8”
23mm
24mm - 15/16”
25mm
26mm - 1”
27mm - 1 1/16”
28mm
29mm - 1 1/8”
30mm - 1 3/16”
31mm 
32mm - 1 1/4”
33mm - 1 5/16”
34mm
35mm - 1 3/8”
36mm
37mm - 1 7/16”
38mm - 1 1/2”
39mm
40mm - 1 9/16”
41mm - 1 5/8”
42mm
43mm - 1 11/16”
44mm - 1 3/4”
45mm
46mm - 1 13/16”
47mm
48mm - 1 7/8”
49mm - 1 15/16”
50mm
51mm - 2”
52mm - 2 1/16”
53mm
54mm - 2 1/8”
55mm
56mm - 2 3/16”
57mm - 2 1/4”
58mm
59mm - 2 5/16”
60mm - 2 3/8”
61mm
62mm - 2 7/16”
63mm
64mm - 2 1/2”
65mm - 2 9/16”
66mm
67mm - 2 5/8”
68mm - 2 11/16”
69mm
70mm - 2 3/4”
71mm - 2 13/16”
72mm
73mm - 2 7/8”
74mm
75mm - 2 15/16”
76mm - 3”