AWG Wire Sizes
Electrical & Wiring · 10 specs
Direct Answer
The American Wire Gauge (AWG / ASTM B258) system standardizes solid round electrical conductor diameters based on a logarithmic ratio where 36 AWG equals 0.0050 inches (0.127 mm) and 4/0 (0000) AWG equals 0.4600 inches (11.684 mm) across 39 stepping steps.
Source: ASTM B258-18 Standard Specification for Standard Nominal Diameters / NEC Table 8 · Last reviewed Aug 28, 2026
Specs
| Governing Standards | ASTM B258 / National Electrical Code (NEC) Chapter 9 Table 8 |
| Geometric Stepping Ratio | Ratio between consecutive gauges is 39√(0.4600 / 0.0050) ≈ 1.1229322 |
| Area Doubling Rule of Thumb | Decreasing by 3 gauge numbers doubles conductor cross-sectional area and halves resistance |
| Diameter Doubling Rule | Decreasing by 6 gauge numbers doubles conductor diameter |
| 14 AWG (15A Residential Lighting) | Dia: 1.628 mm (0.0641 in) | Area: 2.08 mm² (4,110 cmil) | 8.286 Ω/km |
| 12 AWG (20A Small Appliance) | Dia: 2.053 mm (0.0808 in) | Area: 3.31 mm² (6,530 cmil) | 5.211 Ω/km |
| 10 AWG (30A Water Heater / Dryer) | Dia: 2.588 mm (0.1019 in) | Area: 5.26 mm² (10,380 cmil) | 3.277 Ω/km |
| 8 AWG (40-50A Electric Range) | Dia: 3.264 mm (0.1285 in) | Area: 8.37 mm² (16,510 cmil) | 2.061 Ω/km |
| 6 AWG (55-65A Subpanel / Cooktop) | Dia: 4.115 mm (0.1620 in) | Area: 13.30 mm² (26,240 cmil) | 1.296 Ω/km |
| 4/0 AWG (200A Residential Service) | Dia: 11.684 mm (0.4600 in) | Area: 107.2 mm² (211,600 cmil) | 0.1608 Ω/km |
Complete AWG Copper Conductor Specification Matrix
| AWG Size | Conductor Diameter (mm) | Conductor Diameter (Inches) | Cross-Section Area (mm²) | Circular Mils (cmil) | DC Resistance (Ω/km @ 20°C) |
|---|---|---|---|---|---|
| 4/0 (0000) | 11.684 mm | 0.4600" | 107.22 mm² | 211,600 | 0.1608 Ω/km |
| 3/0 (000) | 10.404 mm | 0.4096" | 85.01 mm² | 167,800 | 0.2028 Ω/km |
| 2/0 (00) | 9.266 mm | 0.3648" | 67.43 mm² | 133,100 | 0.2557 Ω/km |
| 1/0 (0) | 8.252 mm | 0.3249" | 53.49 mm² | 105,600 | 0.3224 Ω/km |
| 2 AWG | 6.544 mm | 0.2576" | 33.62 mm² | 66,360 | 0.5127 Ω/km |
| 4 AWG | 5.189 mm | 0.2043" | 21.15 mm² | 41,740 | 0.8152 Ω/km |
| 6 AWG | 4.115 mm | 0.1620" | 13.30 mm² | 26,240 | 1.296 Ω/km |
| 8 AWG | 3.264 mm | 0.1285" | 8.37 mm² | 16,510 | 2.061 Ω/km |
| 10 AWG | 2.588 mm | 0.1019" | 5.26 mm² | 10,380 | 3.277 Ω/km |
| 12 AWG | 2.053 mm | 0.0808" | 3.31 mm² | 6,530 | 5.211 Ω/km |
| 14 AWG | 1.628 mm | 0.0641" | 2.08 mm² | 4,110 | 8.286 Ω/km |
| 16 AWG | 1.291 mm | 0.0508" | 1.31 mm² | 2,580 | 13.17 Ω/km |
| 18 AWG | 1.024 mm | 0.0403" | 0.823 mm² | 1,620 | 20.95 Ω/km |
Mathematical Basis of the AWG Scale
The AWG system was developed in 1857 by J.R. Brown based on the number of drawing dies required to reduce heavy rod down to fine wire:
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Exact ASTM Diameter Formula: For gauge number n (where 1/0 = 0, 2/0 = -1, 3/0 = -2, 4/0 = -3): d_n = 0.005 × 92³6–n/39 inches = 0.127 × 92³6–n/39 mm
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Circular Mils (cmil): In US electrical practice, cross-sectional area is expressed in circular mils, defined as the area of a circle with a diameter of 1 mil (0.001 in). Therefore: Area(cmil) = (d in mils)².