AWG – American wire gauge
Wire sizes and strand sizes (for non-ferrous metals) can be indicated in two ways on the international level: in mm or as AWG. While the actual diameter is used within the metric system, the so-called AWG system represents a codification based on the number of manufacturing steps required.
Definition of "AWG"
AWG is an acronym for "American Wire Gauge" (German translation: "Amerikanische Drahtlehre"). As you may have already concluded, this coding system originates from North America. It reflects a geometric sequence that was introduced in the middle of the 19th century by Joseph Rogers Brown for use in his tool-making company Brown & Sharpe.
The AWG standardized wire gauge system is used to plot diameters and cross-sections of electrical conductors made out of non-ferrous metals, applied to both wires and strands. The AWG graduation is based on the number of drawing steps required to produce a certain diameter. In order for the wire to arrive at the desired diameter, a fairly thick base wire (e.g. 0.8 mm) is drawn through the tapered mouth of a drawing die. Reducing the diameter only works very gradually, i.e. by means of several drawing steps, with the mouths that are used getting smaller and smaller until the final diameter is obtained.
AWG calculation base
The AWG system clearly defines the range 0000 (4/0) to 36, where all sizes in between adhere to a geometric sequence that comply with the following rule: the AWG figure is a function of the number of drawing steps resulting in ever-decreasing diameters. Even sizes below AWG36 follow the same pattern as they are derived from the size range initially covered.
The unit of the diameter is
in resp. mils = in * 1,000
Cross-sections above 4/0 are indicated in cmils
Single-wire diameter (d)
The ratio between diameters and corresponding AWG sizes can be found in ASTM B 258-02:
As opposed to the usual way of calculating a circular area (single-wire cross-section in mm) according to the formula
This leads to an AWG cross-section stated in "circular mil area" cma = (d mils)2.
AWG36 = 0.005 in = 5 mils
(5 mils)² = 25 cma
the AWG system features a simplified calculation usingd².