AWG area used in the calculators
How do you calculate wire size?
The size of an electrical conductor refers to its cross-sectional area (measured in circular mils (CM) or AWG in the US). The larger the cross-sectional area, the more current the wire can transmit with lower resistance—very similar to water flowing through a wider pipe with less pressure loss. We derive the required conductor area from Ohm's law and conductor resistivity:
where:
- V_drop – Voltage drop calculated between the supply source and the farthest end of the wire, measured in volts (V_drop = V_source × (% drop ÷ 100));
- I – Maximum current running through the conductor, measured in amps (convert power using the watts to amps calculator);
- K – Specific resistance constant of the conductor material at 75°C (12.9 Ω·CM/ft for copper and 21.2 Ω·CM/ft for aluminum);
- L – One-way length of the wire run from panel to load, measured in feet; and
- CM – Cross-sectional area of the conductor, measured in circular mils (where 1,000 CM = 1 kcmil).
Calculating wire sizes for three-phase AC
For a balanced three-phase AC circuit, three current-carrying phase conductors are used instead of a two-wire loop. The calculator accepts line-to-line voltage and line current, modifying the required area of a single conductor to:
The factor of √3 ≈ 1.732 converts between phase and line quantities in a balanced three-phase system, replacing the factor of 2. The calculator automatically selects the next AWG size up from its listed 14 AWG – 4/0 table so the voltage-drop limit is never exceeded. To check apparent power feeding that circuit, use the kVA to amps calculator.
| AWG | Circular mils | Relative area vs. 14 AWG |
|---|---|---|
| 14 | 4,110 | 1.00× |
| 12 | 6,530 | 1.59× |
| 10 | 10,380 | 2.53× |
| 8 | 16,510 | 4.02× |
| 6 | 26,240 | 6.38× |
| 4 | 41,740 | 10.16× |
| 3 | 52,620 | 12.80× |
| 2 | 66,360 | 16.15× |
| 1 | 83,690 | 20.36× |
| 1/0 | 105,600 | 25.69× |
| 2/0 | 133,100 | 32.38× |
| 3/0 | 167,800 | 40.83× |
| 4/0 | 211,600 | 51.48× |
How to map a formula result
If a calculation requires 21,500 circular mils, 8 AWG at 16,510 is too small by area and 6 AWG at 26,240 is the first listed candidate. Never round to the numerically closest AWG when that size falls below the requirement.
The chart is not an ampacity table. Equal AWG conductors can have different permitted ampacity because material, insulation, terminals, ambient temperature and conductor grouping matter.
Common reading mistakes
- Assuming 12 AWG is larger than 10 AWG because 12 is the larger number
- Treating circular-mil area as insulated cable diameter
- Rounding down to a smaller conductor
- Using an AWG chart as a substitute for ampacity rules
- Assuming stranded and solid products have the same outside dimensions
Use area for calculation, product data for installation
Circular mils make formula comparisons consistent. Raceway fill, lug fit, bending space and pulling limits require the actual manufacturer's conductor dimensions and equipment listings.