What is AWG (American Wire Gauge)?
AWG is the standardized US wire-sizing system. Each gauge number represents the conductor diameter — smaller numbers mean larger conductors.
AWG (American Wire Gauge) is the standardized US system for designating round, solid, non-ferrous electrical conductor sizes. Each gauge corresponds to a specific cross-sectional area and diameter. The system is also called Brown & Sharpe gauge (B&S) after the 19th-century instrument-makers who codified it.
How the AWG number works
The AWG number is essentially a count of how many times the wire was drawn through progressively smaller dies during manufacturing. More draws → smaller wire → higher number.
- 14 AWG underwent many draws → small (used for 15A residential branches)
- 6 AWG underwent fewer draws → larger (used for 60A circuits)
- 4/0 AWG underwent even fewer → very large (used for 200A service)
Standard AWG sizes used in NEC wiring
| Gauge | Diameter (mil) | Area (CM) | Common use |
|---|---|---|---|
| 14 | 64.1 | 4,107 | 15A residential branches |
| 12 | 80.8 | 6,530 | 20A residential branches |
| 10 | 101.9 | 10,380 | 30A circuits (dryers, water heaters) |
| 8 | 128.5 | 16,510 | 40A circuits |
| 6 | 162.0 | 26,240 | 60A circuits |
| 4 | 204.3 | 41,740 | 70-85A circuits |
| 3 | 229.4 | 52,620 | 100A circuits |
| 2 | 257.6 | 66,360 | 100-115A circuits |
| 1 | 289.3 | 83,690 | 130A circuits |
| 1/0 | 324.9 | 105,600 | 150A feeders |
| 2/0 | 364.8 | 133,100 | 175A feeders |
| 3/0 | 409.6 | 167,800 | 200A feeders |
| 4/0 | 460.0 | 211,600 | 200-230A feeders |
CM = circular mils. 1 CM = the area of a 1-mil-diameter circle.
Above 4/0, sizes are designated in kcmil (thousands of circular mils): 250, 300, 350, 400, 500, 600, 700, 750, 800, 900, 1000 kcmil. See kcmil explained.
AWG to metric (mm²) conversion
NEC Table 5 lists conductor cross-sectional area in both in² and mm² for fill calculations. Common approximations:
| AWG | mm² (approx) |
|---|---|
| 14 | 2.08 |
| 12 | 3.31 |
| 10 | 5.26 |
| 8 | 8.37 |
| 6 | 13.3 |
| 4 | 21.2 |
| 2 | 33.6 |
| 1/0 | 53.5 |
| 4/0 | 107 |
Use the AWG to mm² converter for exact values.
AWG and ampacity (NEC Table 310.16)
The smaller the AWG number, the more current the conductor can carry. The full ampacity table is at NEC 310.16; a quick view:
| AWG copper | 90°C ampacity |
|---|---|
| 14 | 25A |
| 12 | 30A |
| 10 | 40A |
| 8 | 55A |
| 6 | 75A |
| 4 | 95A |
| 2 | 130A |
| 1/0 | 170A |
| 4/0 | 260A |
The 90°C value is the absolute ceiling. Practical ampacity depends on the terminal temperature rating (60°C or 75°C in most equipment), conductor count derating (NEC 310.15(C)(1)), and ambient correction.
AWG vs SWG vs metric (mm²)
- AWG (American Wire Gauge): US standard
- SWG (Standard Wire Gauge): British / Commonwealth — different number-to-diameter mapping
- Metric (mm²): Cross-sectional area in square millimeters, used in IEC/EU/most of the world
For comparison:
- 12 AWG ≈ 3.31 mm² (US 20A branch)
- 2.5 mm² ≈ 13 AWG (EU 16A branch)
- 4 mm² ≈ 11 AWG (EU 20A branch)