How to Calculate the Size of an Electrical Cable
- 1). Obtain the wire that you will be using. Look to see what the AWG is for that wire. This is usually found on the wire itself, printed sideways along the insulation, or on the packaging for the wire.
- 2). Calculate the diameter of your wire using the following formula: D = [92^((36-AWG)/39)]*.005, where D is the diameter and AWG is the gauge of the wire. The result will be in inches. For example, using a 10-gauge wire, the formula would be as follows: D = [92^((36-10)/39)]*.005 = 0.101897 inches. For the very large wires that have gauges of 0, 00, and 000, use -1, -2, and -3 for the AWG variable in the equation.
- 3). Convert the answer from Step 2 to mils by multiplying the number of inches by 1000. Most wires are too small for inches to be used. In the example: 0.101897in * 1000 = 101.897mils. 1 mil = 1/1000 inch.
- 4). Calculate the cross-sectional area of your wire or cable by squaring the answer from Step 3. In the example: 101.897mils ^ 2 = 10383.0221 circular mils. 1 circular mil = the area of a circle with a diameter of 1 mil. This number is often expressed in kcmils, which is obtained by dividing circular mils by 1000. In the example, 10383.0221/1000 = 10.4 kcmils. 1 kcmil = 1/1000 circular mil.
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