In the electrical industry, wires are commonly referred to by their American Wire Gauge (AWG) number. This number relates to the diameter of the conductor, or how much current it can safely carry. The higher the AWG number, the smaller the diameter and the thinner the wire. This is especially important when choosing a wire that will be used for high amperage applications like residential or business wiring, extension cords and other power-related cables. A wire with a too small diameter may overheat and melt, potentially damaging the system or equipment it is connected to.
The AWG system was established in the 19th century to standardize wire sizes and provide consistency across different manufacturers. While it is still widely used in the United States, most other countries use a metric system to measure conductor size. Both systems measure the same properties of a wire, including its resistance, current carrying capacity and flexibility.
Conductor sizing is often referred to in terms of AWG, diameter, circular mils and cross sectional area (CSA). The AWG system defines the size of single-stranded, solid copper wire. The chart below can be used to convert AWG to square mm wire size.
To calculate the AWG wire size of a stranded conductor, you must know its diameter and number of strands. This information can be found on the label of the cable or by calculating the equivalent cross sectional copper area in the table above. A wire with more strands has a larger diameter than a solid wire of the same AWG size.
When you look at the awg wire size chart, you will notice that there is a direct relationship between the AWG size and its diameter. The largest AWG wire is No. 36, while the smallest is No. 0000. The difference in their diameters is 0.005 inches and 0.46 inches, respectively. There are 40 AWG gauges between these two, or 39 steps. The reason for these geometric steps is that each step decrease in AWG size increases the diameter of the conductor by a fixed ratio.
Another way to calculate the AWG wire size of a multi-stranded conductor is to divide the conductor’s total copper area by its AWG size. This will give you the stranded wire’s equivalent AWG size in circular mils. Then, locate the row in this awg wire size chart that matches your calculation. The corresponding circle in the table represents the diameter of your stranded conductor in circular mils.