Wire Gauge Chart — Wire Sizing Chart
Every AWG and kcmil size with diameter, area, resistance and estimated amp capacity, computed from the ASTM B258 gauge formula.
Quick answer
AWG and kcmil gauge chart
Diameter is the bare conductor. Resistance is DC at 75 °C. Amps is the estimated 75 °C copper ampacity at 30 °C ambient.
| Size | Diameter (in) | Diameter (mm) | Circular mils | Area (mm²) | Ω / 1000 ft (Cu) | Est. amps (Cu 75 °C) | THHN OD (in) |
|---|---|---|---|---|---|---|---|
| 18 AWG | 0.0403 | 1.024 | 1,624 | 0.82 | 6.3861 | 10 A | 0.084 |
| 16 AWG | 0.0508 | 1.290 | 2,583 | 1.31 | 4.0151 | 13 A | 0.096 |
| 14 AWG | 0.0641 | 1.628 | 4,107 | 2.08 | 2.5252 | 18 A | 0.111 |
| 12 AWG | 0.0808 | 2.052 | 6,530 | 3.31 | 1.5882 | 24 A | 0.130 |
| 10 AWG | 0.1019 | 2.588 | 10,383 | 5.26 | 0.9988 | 32 A | 0.164 |
| 8 AWG | 0.1285 | 3.264 | 16,510 | 8.37 | 0.6282 | 44 A | 0.216 |
| 6 AWG | 0.1620 | 4.115 | 26,251 | 13.30 | 0.3951 | 59 A | 0.254 |
| 4 AWG | 0.2043 | 5.189 | 41,741 | 21.15 | 0.2485 | 80 A | 0.324 |
| 3 AWG | 0.2294 | 5.827 | 52,635 | 26.67 | 0.1970 | 93 A | 0.352 |
| 2 AWG | 0.2576 | 6.543 | 66,371 | 33.62 | 0.1563 | 108 A | 0.384 |
| 1 AWG | 0.2893 | 7.348 | 83,693 | 42.41 | 0.1239 | 126 A | 0.446 |
| 1/0 AWG | 0.3249 | 8.252 | 105,535 | 53.49 | 0.0983 | 146 A | 0.486 |
| 2/0 AWG | 0.3648 | 9.266 | 133,077 | 67.43 | 0.0779 | 170 A | 0.532 |
| 3/0 AWG | 0.4096 | 10.404 | 167,806 | 85.01 | 0.0618 | 198 A | 0.581 |
| 4/0 AWG | 0.4600 | 11.684 | 211,600 | 107.22 | 0.0490 | 230 A | 0.642 |
| 250 kcmil | 0.5000 | 12.700 | 250,000 | 126.68 | 0.0415 | 257 A | 0.711 |
| 300 kcmil | 0.5477 | 13.912 | 300,000 | 152.00 | 0.0346 | 289 A | 0.766 |
| 350 kcmil | 0.5916 | 15.027 | 350,000 | 177.34 | 0.0296 | 319 A | 0.817 |
| 400 kcmil | 0.6325 | 16.065 | 400,000 | 202.71 | 0.0259 | 348 A | 0.864 |
| 500 kcmil | 0.7071 | 17.960 | 500,000 | 253.35 | 0.0207 | 403 A | 0.949 |
| 600 kcmil | 0.7746 | 19.675 | 600,000 | 304.03 | 0.0173 | 454 A | 1.051 |
| 750 kcmil | 0.8660 | 21.996 | 750,000 | 380.01 | 0.0138 | 524 A | 1.158 |
Source & method: Diameter, circular mils and resistance are exact computed values. Ampacity is modelled — see the methodology page.
Gauge step relationships
| Change | Diameter | Area / circular mils | Resistance |
|---|---|---|---|
| 1 gauge smaller number | ×1.123 | ×1.261 | ×0.793 |
| 3 gauges smaller number | ×1.416 | ×2.005 | ×0.499 |
| 6 gauges smaller number | ×2.005 | ×4.020 | ×0.249 |
| 10 gauges smaller number | ×3.249 | ×10.556 | ×0.095 |
These ratios are why "go up two sizes for a long run" is such a common rule of thumb: two steps cut resistance by roughly 37%, which cuts voltage drop by the same proportion. Check it on a real run.
Using this wire sizing chart on a real circuit
American Wire Gauge is the sizing system for solid and stranded round conductors in North America, so the same cable gauge chart covers building wire, appliance cord, speaker cable and automotive wiring. The numbering is inverted by design: it counts the drawing operations needed to reach the diameter, which is why 14 AWG is thinner than 10 AWG and why the sizes above 1 AWG continue as 1/0 through 4/0 before switching to kcmil.
As a wire sizing chart, the amp column is a starting point, not the answer. Three things move it. Insulation temperature rating sets the ceiling — 60, 75 or 90 °C. Ambient temperature pulls it down: the same conductor in a 40 °C attic carries roughly 9% less than at 30 °C, and at 50 °C it loses around 25%. Bundling more than three current-carrying conductors in one raceway derates it further.
Typical residential practice follows straight from the chart. Lighting circuits and receptacles on 15 A use 14 AWG copper; 20 A kitchen and general-purpose circuits use 12 AWG; a 30 A dryer or water heater uses 10 AWG; ranges and subpanels move into 8, 6 and larger. Aluminium in the same slot goes up one to two gauge steps for the same load.
For metric comparison the mm² column is the honest way to cross-reference: 14 AWG is about 2.1 mm², 12 AWG is 3.3 mm², 10 AWG is 5.3 mm² and 6 AWG is 13.3 mm². IEC 60228 sizes never match AWG exactly, so pick the next larger mm² size rather than the closest one. On long runs check resistance, not just gauge — voltage drop usually decides the final size.
Frequently asked
- How is AWG wire gauge defined?
- AWG is a geometric series. 36 AWG is 0.005 inches and 4/0 AWG is 0.46 inches, with 39 steps between them. Each step multiplies the diameter by the 39th root of 92, about 1.1229, so the diameter formula is 0.005 × 92^((36 − n) / 39) inches.
- Does a bigger AWG number mean a bigger wire?
- No, it is the opposite. Smaller AWG numbers are larger conductors. 10 AWG is thicker than 14 AWG. Above 1 AWG the sizes continue as 1/0, 2/0, 3/0 and 4/0, then switch to kcmil.
- How much does wire diameter change per gauge step?
- One gauge step changes the diameter by about 12.2% and the cross-sectional area by about 26%. Three gauge steps roughly double the area, and six steps roughly double the diameter.
- What is a circular mil?
- A circular mil is the area of a circle one mil (0.001 inch) in diameter. Circular mils equal the diameter in mils squared, which makes area comparisons between gauges simple arithmetic.
- What does kcmil mean?
- kcmil is thousands of circular mils, used for conductors larger than 4/0 AWG. A 250 kcmil conductor has 250,000 circular mils of cross-section, about 19% more than 4/0.
Related charts & calculators
- Ampacity ChartEstimated allowable ampacity by conductor size, material and insulation rating.
- Wire Size ChartWhat size wire for each breaker rating and typical circuit.
- kcmil Wire Size ChartMCM to AWG conversion, circular mils, resistance and ampacity for 250-750 kcmil.
- Conduit Fill ChartMaximum THHN conductors per trade size for every raceway type.
- EMT Conduit Fill ChartConductor counts and internal areas for electrical metallic tubing.
- PVC Conduit Fill ChartSchedule 40 and Schedule 80 conductor counts and usable areas.