Wire gauge measures how large a wire's cross sectional area is. Knowing the gauge is important because it determines how much electric current a wire can carry without being damaged—this quantity is called ampacity.
The American Wire Gauge system or AWG standardizes the cross sectional area of a wires by assigning them an AWG number. As seen in Figure 1, a lower numbered gauge wire has a larger diameter and thus is able to carry higher currents. There are a total of 40 different gauge sizes with cross sectional areas ranging from 0.013 mm2 to 107.22 mm2 with their diameters changing incrementally between each gauge number.
|AWG number||Cross sectional area (mm2)||Ohms/km (/km)||Ampacity (A)||Usage example|
|18||0.82||20.95||14||Low voltage lighting|
|6||13.30||1.30||75||Large electric heaters|
|3||26.67||0.65||115||Large commercial wiring|
|2||33.63||0.51||130||Car battery cable|
The figures above are taken from Table 310.15(B)(16) in the 2014 National Electrical Code (USA) and assume a temperature rating of 90°C. Also, Table 3.1 on page 69 in Introduction to Electricity was used as a template and reference.
For a more complete list, please see Dr. Rowlett's unit page.
For further information please see the related pages below: