AWG wire size chart
| AWG | Diameter (in) | Diameter (mm) | Area (mm²) | Area (kcmil) | Ω/1,000 ft at 20 °C |
|---|---|---|---|---|---|
| 4/0 | 0.4600 | 11.684 | 107 | 212 | 0.04901 |
| 3/0 | 0.4096 | 10.405 | 85.0 | 168 | 0.06180 |
| 2/0 | 0.3648 | 9.266 | 67.4 | 133 | 0.07793 |
| 1/0 | 0.3249 | 8.251 | 53.5 | 106 | 0.09827 |
| 1 | 0.2893 | 7.348 | 42.4 | 83.7 | 0.1239 |
| 2 | 0.2576 | 6.544 | 33.6 | 66.4 | 0.1563 |
| 3 | 0.2294 | 5.827 | 26.7 | 52.6 | 0.1970 |
| 4 | 0.2043 | 5.189 | 21.2 | 41.7 | 0.2485 |
| 5 | 0.1819 | 4.621 | 16.8 | 33.1 | 0.3133 |
| 6 | 0.1620 | 4.115 | 13.3 | 26.3 | 0.3951 |
| 7 | 0.1443 | 3.665 | 10.5 | 20.8 | 0.4982 |
| 8 | 0.1285 | 3.264 | 8.37 | 16.5 | 0.6282 |
| 9 | 0.1144 | 2.906 | 6.63 | 13.1 | 0.7921 |
| 10 | 0.1019 | 2.588 | 5.26 | 10.4 | 0.9989 |
| 11 | 0.0907 | 2.305 | 4.17 | 8.23 | 1.260 |
| 12 | 0.0808 | 2.053 | 3.31 | 6.53 | 1.588 |
| 13 | 0.0720 | 1.828 | 2.62 | 5.18 | 2.003 |
| 14 | 0.0641 | 1.628 | 2.08 | 4.11 | 2.525 |
| 15 | 0.0571 | 1.450 | 1.65 | 3.26 | 3.184 |
| 16 | 0.0508 | 1.291 | 1.31 | 2.58 | 4.016 |
| 17 | 0.0453 | 1.150 | 1.04 | 2.05 | 5.064 |
| 18 | 0.0403 | 1.024 | 0.823 | 1.62 | 6.385 |
| 19 | 0.0359 | 0.912 | 0.653 | 1.29 | 8.051 |
| 20 | 0.0320 | 0.812 | 0.518 | 1.02 | 10.15 |
| 21 | 0.0285 | 0.723 | 0.410 | 0.810 | 12.80 |
| 22 | 0.0253 | 0.644 | 0.326 | 0.642 | 16.14 |
| 23 | 0.0226 | 0.573 | 0.258 | 0.509 | 20.36 |
| 24 | 0.0201 | 0.511 | 0.205 | 0.404 | 25.67 |
| 25 | 0.0179 | 0.455 | 0.162 | 0.320 | 32.37 |
| 26 | 0.0159 | 0.405 | 0.129 | 0.254 | 40.81 |
| 27 | 0.0142 | 0.361 | 0.102 | 0.202 | 51.47 |
| 28 | 0.0126 | 0.321 | 0.0810 | 0.160 | 64.90 |
| 29 | 0.0113 | 0.286 | 0.0642 | 0.127 | 81.84 |
| 30 | 0.0100 | 0.255 | 0.0509 | 0.101 | 103.2 |
Solid round copper, from the ASTM B258 formula. Stranded wire of the same gauge has about the same area but a slightly larger outside diameter and a little more resistance.
How the numbers are worked out
- Diameter = 0.005 in × 92(36 − n)/39, where n is the gauge number and 1/0, 2/0, 3/0, 4/0 count as 0, −1, −2, −3. So 36 AWG is 0.005 in and 4/0 is 0.46 in.
- Area: kcmil = (diameter in thousandths of an inch)² ÷ 1,000; mm² = π/4 × (diameter in mm)².
- Resistance = 1/58 Ω·mm²/m (annealed copper, 20 °C) ÷ area, raised 0.393% per °C above 20 °C. At 75 °C this matches the NEC Chapter 9 Table 8 values for solid wire (12 AWG ≈ 1.93 Ω/1,000 ft); stranded conductors, used for the larger sizes, run slightly higher.
- Voltage drop = 2 × one-way length × current × resistance per foot for single-phase or DC; √3 instead of 2 for three-phase, as a share of the line-to-line voltage.
The 3% (branch) and 5% (feeder plus branch) figures come from informational notes in NEC 210.19(A) and 215.2(A) — design advice for efficiency, not requirements.
What this page doesn't cover
- Ampacity — the current a wire may carry depends on insulation rating, terminal rating, ambient temperature and bundling (NEC 310.16, 110.14(C)).
- Aluminum conductors, AC skin effect and reactance on large feeders, and power factor.
For color-banded resistors use the resistor color code calculator; for other unit conversions, the unit converter.
Frequently asked questions
How thick is 12 gauge wire?
12 AWG solid wire is 0.0808 in (2.053 mm) across, with a cross-section of 3.31 mm² (6.53 kcmil). Solid copper 12 AWG has about 1.588 Ω per 1,000 ft at 20 °C.
How do I calculate voltage drop?
For a single-phase or DC circuit, drop = 2 × one-way length × current × resistance per foot (the current goes out and back). For three-phase, use √3 instead of 2. 50 ft of 12 AWG copper at 15 A and 75 °C drops about 2.9 V — 2.4% of 120 V.
What voltage drop is acceptable?
The National Electrical Code suggests no more than 3% on a branch circuit and 5% for feeder plus branch combined. That is an informational note for efficiency, not an enforceable rule — but it is the usual design target.
Why does the gauge number go down as the wire gets bigger?
AWG numbers come from wire-drawing steps: each smaller number is one fewer pass through a die. Every 6 gauges roughly halves the diameter, and every 3 gauges roughly halves the area.
Does this tell me what size wire I need for my breaker?
No. Ampacity depends on the insulation temperature rating, the terminals and how many conductors share a raceway (NEC 310.16 and 110.14(C)). Use this page for size, resistance and voltage drop, and check ampacity in the code table or with an electrician.