AWG To Circular Mils Chart (For 4/0 AWG To 20 AWG)

Wire size can be expressed as both gauge number (American Wire Gauge or AWG) or circular mils. In many cases, we will have to convert AWG to circular mils. To help you out, we will look into AWG to circular mils formula to show how the conversion is made. Further on, you will also find an AWG To Circular Mils Chart with 20 AWG to 4/0 AWG wires converted to circular mils.

Let’s first look at both of these units of the size of the wires:

  • AWG stands for American Wire Gauge. We have been using AWG since 1857; it is the first geometrical wire gauge system for conducting wires (both copper and aluminum wires). It is basically a measure of wire thickness (diameter). The slimmest 40 AWG wire is 0.005 inches in diameter, and the thickest 4/0 wire has a diameter of 0.46 inches (that’s almost a 100x difference).
  • Circular mil is a unit for the cross-section of the wire. 1 circular mil is equal to an area of a circle with 1-mil diameter (1 mil = 1/1000 inch or about 5.06 10-4 mm2). Circular mil is a very small unit compared to AWG; we will in the chart that 20 AWG wire already has 1,022 circular mils. 0 AWG wire has over 100,000 circular mils.
awg vs circular mils
We measure the diameter of a wire in AWG, and the cross-section of a wire in circular mils (cmil for short)

So, basically, we are converting units of wire thickness (AWG) to units of wire cross-section (circular mils). Both units are a bit complex (AWG is even a logarithmic scale). That also means that the formula for converting AWG to circular mils will be quite complex. Here is the equation that converts AWG to circular mils:

Circular Mils = (5 × 92(36 – AWG)/39)2 (Source: Wikipedia)

To calculate how many circular mils is 12 AWG wire, for example, you just need to insert ’12’ in the equation, and you get the circular mills. As you can see, this is quite a complex equation, so this calculation is easier said than done. That’s why it’s much easier to consult the AWG To Circular Mils Chart further on, but let’s solve this case just to illustrate how this equation works:

Circular Mils (12 AWG) = (5 × 92(36 – 12)/39)2 = 6,530 Circular Mils

As we can see, 12 AWG wire (measure of cross-section, or current carrying capability) has a diameter of 6,530 circular mills. This is very useful information when calculating 12 AWG wire voltage drop at a distance, for example.

Note: There is no difference between copper and aluminum wires when it comes to AWG and circular mils. These are pure measures of cross-section and diameter; the difference in the amps copper vs. aluminum wire can handle comes down to the resistivity of each metal.

This was just one example. Here is the whole chart, followed by a few tips on how to figure out AWG to circular mils conversion on the go:

AWG To Circular Mils

AWG Number: Circular Mils:
0000 (4/0) AWG 211,592 Circular Mils
000 (3/0) AWG 167,800 Circular Mils
00 (2/0) AWG 133,072 Circular Mils
0 (1/0) AWG 105,531 Circular Mils
1 AWG 83,690 Circular Mils
2 AWG 66,369 Circular Mils
3 AWG 52,633 Circular Mils
4 AWG 41,740 Circular Mils
5 AWG 33,101 Circular Mils
6 AWG 26,251 Circular Mils
7 AWG 20,818 Circular Mils
8 AWG 16,509 Circular Mils
9 AWG 13,092 Circular Mils
10 AWG 10,383 Circular Mils
11 AWG 8,234 Circular Mils
12 AWG 6,530 Circular Mils
13 AWG 5,178 Circular Mils
14 AWG 4,107 Circular Mils
15 AWG 3,257 Circular Mils
16 AWG 2,583 Circular Mils
17 AWG 2,048 Circular Mils
18 AWG 1,624 Circular Mils
19 AWG 1,290 Circular Mils
20 AWG 1,022 Circular Mils

As you can see, here are some rough rules of thumbs we can easily notice from this chart. Namely:

  • 20 AWG to about 10 AWG wires have a diameter of about 1,000 to 10,000 circular mils.
  • 10 AWG to 0 AWG wires have a diameter of about 10,000 to 100,000 circular mils.
  • The biggest AWG wire (4/0 AWG) is equal to 211,592 circular mils (this could be called 211 kcmil wire). The next wire by thickness is called 250 kcmil wire. We go from AWG directly to thousands of circular mils (abbreviated as kcmil). You can check the AWG to kcmil relationship here.
  • From the thin 20 AWG wire to the thicker wires, we see that each consecutive wire has a 26.1% bigger diameter. Example: 15 AWG wire has a 3,257 cmil diameter, and 14 AWG gas has a 4,107 cmil diameter. That’s a 26.1% increase. This is true for any two AWG wires.

Circular mils appear in many current-carrying equations. The most prominent one is the voltage drop equation. Hopefully, with this AWG to cmil chart, you can now easily make this conversion. If you need any help, you can use the comment section below, explain what you want to solve, and we will help you out as best we can.

Leave a Comment