Electrical
Wire Gauge, Circular Mils, and Area
Circular mil area and approximate insulated cross-sectional area for AWG and kcmil conductor sizes.
Source of these values
Circular mil values are the standard AWG geometric definitions. Insulated areas are the approximate values commonly published for THHN and THWN-2 in NFPA 70 Chapter 9 Table 5.
| Size | Circular mils | THHN area, sq in | Relative area |
|---|---|---|---|
| 14 | 4,110 | 0.0097 | 0.6x of 12 AWG |
| 12 | 6,530 | 0.0133 | 1.0x of 12 AWG |
| 10 | 10,380 | 0.0211 | 1.6x of 12 AWG |
| 8 | 16,510 | 0.0366 | 2.5x of 12 AWG |
| 6 | 26,240 | 0.0507 | 4.0x of 12 AWG |
| 4 | 41,740 | 0.0824 | 6.4x of 12 AWG |
| 3 | 52,620 | 0.0973 | 8.1x of 12 AWG |
| 2 | 66,360 | 0.1158 | 10.2x of 12 AWG |
| 1 | 83,690 | 0.1562 | 12.8x of 12 AWG |
| 1/0 | 105,600 | 0.1855 | 16.2x of 12 AWG |
| 2/0 | 133,100 | 0.2223 | 20.4x of 12 AWG |
| 3/0 | 167,800 | 0.2679 | 25.7x of 12 AWG |
| 4/0 | 211,600 | 0.3237 | 32.4x of 12 AWG |
| 250 kcmil | 250,000 | 0.3970 | 38.3x of 12 AWG |
| 300 kcmil | 300,000 | 0.4608 | 45.9x of 12 AWG |
| 350 kcmil | 350,000 | 0.5242 | 53.6x of 12 AWG |
| 400 kcmil | 400,000 | 0.5863 | 61.3x of 12 AWG |
| 500 kcmil | 500,000 | 0.7073 | 76.6x of 12 AWG |
| 600 kcmil | 600,000 | 0.8676 | 91.9x of 12 AWG |
| 750 kcmil | 750,000 | 1.0496 | 114.9x of 12 AWG |
| 1000 kcmil | 1,000,000 | 1.3478 | 153.1x of 12 AWG |
In short
Circular mils express conductor cross-sectional area and are the basis of the voltage drop formula. A 12 AWG conductor is 6,530 circular mils, 4/0 AWG is 211,600, and one kcmil is 1,000 circular mils. Each three AWG sizes roughly doubles the area.
Notes and limits
- Insulated areas here are for THHN and THWN-2. The insulated conductor area table lists XHHW, TW, THW and RHW alongside, and using the wrong one changes a conduit fill result.
- Circular mils are used directly in the voltage drop formula. Doubling the circular mils halves the voltage drop at the same current and distance.
Direct contact
Have a controls question?
Reach Eric Sullivan directly about anything on this site, a controls or automation topic, or one of his personal projects.