8 AWG Wire Specs
Ampacity, geometry, resistance, conduit fill and maximum run length for 8 AWG conductors in copper and aluminium.
Quick answer
8 AWG copper carries about 44 A at 75 °C (37 A at 60 °C, 49 A at 90 °C). The bare conductor is 0.1285 in (3.26 mm) and 16,510 circular mils, with 0.6282 Ω per 1000 ft. It pairs with a 40 A breaker at 75 °C terminations.
Copper 75 °C
44A
Aluminium 75 °C
34A
Diameter
0.1285in
Circular mils
16,510
Full specification
| Size designation | 8 AWG |
|---|---|
| AWG gauge number | 8 |
| Circular mils | 16,510 |
| kcmil | 16.51 |
| Bare diameter (in) | 0.1285 |
| Bare diameter (mm) | 3.264 |
| Cross-section (mm²) | 8.37 |
| THHN/THWN-2 OD (in) | 0.216 |
| Insulated area (sq in) | 0.0366 |
| Copper resistance (Ω/1000 ft) | 0.6282 |
| Aluminium resistance (Ω/1000 ft) | 1.0297 |
| Max standard breaker (Cu, 75 °C) | 40 A |
Published standard — source: Geometry computed from the ASTM B258 AWG formula; resistance from standard resistivityFormula estimate — source: Ampacity from the site model
Ampacity with derating
Estimated ampacity from the 90 °C column at various ambient temperatures and conductor counts.
| Conductors in raceway | 30 °C ambient | 40 °C ambient | 50 °C ambient | 60 °C ambient |
|---|---|---|---|---|
| 3 | 49 A | 45 A | 40 A | 35 A |
| 6 | 39 A | 36 A | 32 A | 28 A |
| 9 | 34 A | 31 A | 28 A | 24 A |
| 15 | 25 A | 22 A | 20 A | 17 A |
| 25 | 22 A | 20 A | 18 A | 16 A |
Source & method: The governing value is also capped by the termination rating, commonly 75 °C, which for this size is 44 A. Run your own conditions.
Maximum run length at 3% voltage drop
One-way distance for 8 AWG copper before drop exceeds 3%.
| Load | 120 V 1Ø | 240 V 1Ø | 208 V 3Ø | 480 V 3Ø |
|---|---|---|---|---|
| 10 A | 230 ft | 460 ft | 461 ft | 1,064 ft |
| 15 A | 153 ft | 307 ft | 307 ft | 709 ft |
| 20 A | 115 ft | 230 ft | 230 ft | 532 ft |
| 30 A | 76 ft | 153 ft | 153 ft | 354 ft |
| 40 A | 57 ft | 115 ft | 115 ft | 266 ft |
| 50 A | 46 ft | 92 ft | 92 ft | 212 ft |
How many 8 AWG conductors fit in conduit
Maximum count of this size alone, at the fill percentage matching the resulting count.
| Conduit | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" |
|---|---|---|---|---|---|---|---|---|---|---|
| EMT | 3 | 5 | 9 | 16 | 22 | 36 | 63 | 96 | 126 | 161 |
| IMC | 3 | 6 | 10 | 17 | 24 | 39 | 56 | 86 | 115 | 148 |
| RMC | 3 | 5 | 9 | 16 | 22 | 37 | 53 | 81 | 109 | 140 |
| PVC Sch 40 | 3 | 5 | 9 | 15 | 21 | 35 | 51 | 79 | 106 | 137 |
| PVC Sch 80 | 1 | 4 | 7 | 13 | 18 | 31 | 44 | 70 | 94 | 122 |
Neighbouring sizes
Frequently asked
- How many amps can 8 AWG wire carry?
- 8 AWG copper is estimated at 37 A at 60 °C, 44 A at 75 °C and 49 A at 90 °C, at 30 °C ambient with no more than three current-carrying conductors. Aluminium of the same size is about 34 A at 75 °C.
- What breaker size goes with 8 AWG copper?
- The largest standard overcurrent device that 8 AWG copper supports at 75 °C is 40 A. For a continuous load, the load itself must not exceed 80% of that rating.
- What is the diameter of 8 AWG wire?
- The bare conductor is 0.1285 inches (3.264 mm) in diameter, which is 16,510 circular mils. With THHN/THWN-2 insulation the nominal outside diameter is about 0.216 inches.
- What is the resistance of 8 AWG wire?
- About 0.6282 ohms per 1000 feet for copper and 1.0297 ohms per 1000 feet for aluminium, at 75 °C.
- How far can I run 8 AWG wire?
- Distance depends on load and voltage. At 20 A on a 120 V single-phase circuit, 8 AWG copper stays under 3% voltage drop for about 115 feet one-way. Doubling the voltage roughly doubles the allowable distance.
Materials for this size
Materials for this size
Wire, cable and terminations for 8 AWG.
- THHN/THWN-2 8 AWG copper8 AWG copperBuilding wire in the size this page covers (8 AWG copper).Check price on Amazon →
- NM-B cable 8 AWG8 AWGRomex-type cable for dry indoor branch circuits at this size.Check price on Amazon →
- Wire connectors for 8 AWG8 AWGPush-in or twist-on connectors rated for this conductor size.Check price on Amazon →
- Terminal lugs & anti-oxidantCopper-rated mechanical lugs for panel and disconnect terminations.Check price on Amazon →
Links go to Amazon search results, not a single listing — confirm ratings, insulation type and listing details before buying, and make sure the part is approved for your application.
Related charts & calculators
- Voltage Drop CalculatorPercent drop, end voltage and minimum conductor for any run length.
- Conduit Fill CalculatorFill percentage and maximum conductor count for EMT, RMC, IMC and PVC.
- Breaker Size CalculatorOvercurrent device rating and minimum conductor from load current.
- Wire Ampacity CalculatorDerated ampacity for ambient temperature and bundled conductors.
- Box Fill CalculatorVolume allowances for conductors, clamps, devices and grounds per NEC 314.16.
- Ampacity ChartEstimated allowable ampacity by conductor size, material and insulation rating.