How To… Measure Jump Rings

Determining the interior and outside diameter of jump rings

Some patterns call for jump rings based on their interior diameter (ID). If you only know the outside diameter (OD) of your ring, subtract twice the width of the wire gauge from the OD measurement. For instance, 18 ga wire is about 1.024mm thick. To find the ID of a 5.5mm 18ga jump ring, do the following calculation:

OD – (2 x gauge) = ID
5.5– (2 x 1.024) = 3.452 (about 3.5mm)

conversely, to find Outside Diameter:
ID + (2 x gauge) = OD
3.5 + (2 x 1.024) = 5.548 (about 5.5mm)

Quick gauge-to-millimeter chart:

16ga = 1.291mm
18ga = 1.024 mm
20ga = 0.812 mm
22ga = 0.644 mm
24ga = 0.511mm

from The Bead Scoop Vol. II Issue 2 July 2008