Wire Diameter - Gauge Conversions

The diameter of the wire you buy depends on its country of origin. The two units of measurement in use are the metric system, in which the diameter of the wire is given in millimeters, and the Brown & Sharpe (B&S) gauge number. I live in the United States and the wire I buy is sized according to its gauge. However, many excellent patterns and instructions are available written for wire sized in millimeters. You may live in a country where the wire is in millimeters, yet you want to try a pattern written for gauge wire. What's a jewelry maker to do? Use the size of wire that is closest to the recommended wire. There are no exact conversions, so sometimes you will want to use the slightly finer wire (e.g., when making small jump rings or a delicate design) and sometimes you may choose the closest larger diameter (e.g., when making clasps or components that will be exposed to stress).

Nearest Equivalents - Millimeters and Gauges

Use this table when you simply want the wire that is closest in diameter to the other system of measurement.

Metric Diameter -- Nearest Gauge
2.00 mm -- 12
1.50 mm -- 14
1.25 mm -- 16
1.00 mm -- 18
0.75 mm -- 20
0.64 mm -- 22
0.50 mm -- 24

Metric Diameter of B&S Gauges

Refer to this table when you need to make a judgement call to select the best wire for a purpose. You won't actually get two decimal points of precision in gauge wire, unless you purchased wire conforming to this level of tolerance. You can use vernier calipers if you need to measure the diameter of wire with high precision.

B&S Gauge -- Actual Diameter
12 -- 2.05 mm
14 -- 1.63 mm
16 -- 1.29 mm
18 -- 1.02 mm
20 -- 0.81 mm
22 -- 0.64 mm
24 -- 0.51 mm