Jump ring sizes Metric/English Conversions

The inside diameter of a jump ring is measured by the size of the mandrel used to make it. Some jump-ring manufacturers use mandrels that are measured in fractional inches (like 1/8 in.), while others use mandrels measured in millimeters, which come in quarter-millimeter increments. When choosing jump rings to make a project, this can be confusing. If a project calls for jump rings measured in millimeters, and the store you shop at sells jump rings measured in inches, you may find that there are no rings that perfectly match a straight math conversion (1 in. = 25.5 mm).

 

In this chart, the first figure is the one that the project calls for, if the author used jump rings measured in inches. The number in parentheses following that figure is the exact mathematical conversion to millimeters. The number in the second column is the closest commercially available size in millimeters.