The electrical wiring in your house or workplace is a complex network of wires and cables. Each of them is carrying a significant amount of current, and if any one of them is not properly selected it can cause serious problems like fire or electric shock.
To avoid these problems, the correct size of a wire should be chosen for any application. This is why most engineers use a wire gauge chart, which shows the ampacity (current carrying capacity) of different sizes of wires based on their diameter. The chart also includes other information such as resistance, cross-sectional area and many more.
There are different ways to determine the size of an electrical wire, and many different standards exist worldwide. The most common in the US is the American Wire Gauge (AWG) system, which defines 40 standard wire sizes starting from 0 AWG and ending with 0000 AWG. The smaller the number, the larger the diameter of the wire. It is also possible to use a wire size calculator, which can help determine the size of an electrical wire based on other parameters.
The wire gauge chart explains how to calculate the wire size by using simple formulas. The chart is based on the diameter of a round copper conductor, and the values are valid for nick-free soft annealed wire with a tensile strength of 37000 pounds per square inch. It is important to remember that the rated ampacities in this table are just a rule of thumb, and in careful engineering other factors such as voltage drop, insulation temperature limit, thickness, thermal conductivity, air convection, and other environmental effects must be taken into account.
This chart is also useful in determining the correct number of smaller wires to use when making a cable with a specific AWG size. A cable with multiple smaller wires is called a parallel, and the number of wires in a parallel can be varied depending on the application. For example, a parallel with 2 wires is ideal for lighting circuits, while a parallel with 10 wires may be used to run an AC motor.
The tables in this article are based on the AWG system, which specifies sizes for single, solid and round conductors. For stranded wires, the gauge is determined by the diameter of the equivalent solid conductor, but small gaps between the strands cause it to have a larger overall diameter than a solid wire with the same AWG size. The tables below give the AWG numbers for a round conductor, and the number of smaller wires required to make a particular cable size with that AWG is given in the next column. The wire sizes are given in circular mils, and 1 mil is equal to 0.001 inches (or 0.000507 mm). This chart can be downloaded as a pdf file by clicking on the download button below.