4 AWG Wire Specs
Ampacity, geometry, resistance, conduit fill and maximum run length for 4 AWG conductors in copper and aluminium.
Quick answer
4 AWG copper carries about 80 A at 75 °C (68 A at 60 °C, 90 A at 90 °C). The bare conductor is 0.2043 in (5.19 mm) and 41,741 circular mils, with 0.2485 Ω per 1000 ft. It pairs with a 80 A breaker at 75 °C terminations.
Copper 75 °C
80A
Aluminium 75 °C
62A
Diameter
0.2043in
Circular mils
41,741
Full specification
| Size designation | 4 AWG |
|---|---|
| AWG gauge number | 4 |
| Circular mils | 41,741 |
| kcmil | 41.74 |
| Bare diameter (in) | 0.2043 |
| Bare diameter (mm) | 5.189 |
| Cross-section (mm²) | 21.15 |
| THHN/THWN-2 OD (in) | 0.324 |
| Insulated area (sq in) | 0.0824 |
| Copper resistance (Ω/1000 ft) | 0.2485 |
| Aluminium resistance (Ω/1000 ft) | 0.4073 |
| Max standard breaker (Cu, 75 °C) | 80 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 | 90 A | 82 A | 73 A | 64 A |
| 6 | 72 A | 66 A | 59 A | 51 A |
| 9 | 63 A | 58 A | 51 A | 45 A |
| 15 | 45 A | 41 A | 37 A | 32 A |
| 25 | 41 A | 37 A | 33 A | 29 A |
Source & method: The governing value is also capped by the termination rating, commonly 75 °C, which for this size is 80 A. Run your own conditions.
Maximum run length at 3% voltage drop
One-way distance for 4 AWG copper before drop exceeds 3%.
| Load | 120 V 1Ø | 240 V 1Ø | 208 V 3Ø | 480 V 3Ø |
|---|---|---|---|---|
| 10 A | 582 ft | 1,164 ft | 1,165 ft | 2,690 ft |
| 15 A | 388 ft | 776 ft | 777 ft | 1,793 ft |
| 20 A | 291 ft | 582 ft | 582 ft | 1,345 ft |
| 30 A | 194 ft | 388 ft | 388 ft | 896 ft |
| 40 A | 145 ft | 291 ft | 291 ft | 672 ft |
| 50 A | 116 ft | 232 ft | 233 ft | 538 ft |
How many 4 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 | 1 | 2 | 4 | 7 | 9 | 16 | 28 | 42 | 56 | 71 |
| IMC | 1 | 2 | 4 | 7 | 10 | 17 | 24 | 38 | 51 | 66 |
| RMC | 1 | 2 | 4 | 7 | 10 | 16 | 23 | 36 | 48 | 62 |
| PVC Sch 40 | 1 | 1 | 4 | 7 | 9 | 15 | 22 | 35 | 47 | 60 |
| PVC Sch 80 | 1 | 1 | 3 | 6 | 8 | 13 | 19 | 31 | 42 | 54 |
Neighbouring sizes
Frequently asked
- How many amps can 4 AWG wire carry?
- 4 AWG copper is estimated at 68 A at 60 °C, 80 A at 75 °C and 90 A at 90 °C, at 30 °C ambient with no more than three current-carrying conductors. Aluminium of the same size is about 62 A at 75 °C.
- What breaker size goes with 4 AWG copper?
- The largest standard overcurrent device that 4 AWG copper supports at 75 °C is 80 A. For a continuous load, the load itself must not exceed 80% of that rating.
- What is the diameter of 4 AWG wire?
- The bare conductor is 0.2043 inches (5.189 mm) in diameter, which is 41,741 circular mils. With THHN/THWN-2 insulation the nominal outside diameter is about 0.324 inches.
- What is the resistance of 4 AWG wire?
- About 0.2485 ohms per 1000 feet for copper and 0.4073 ohms per 1000 feet for aluminium, at 75 °C.
- How far can I run 4 AWG wire?
- Distance depends on load and voltage. At 20 A on a 120 V single-phase circuit, 4 AWG copper stays under 3% voltage drop for about 291 feet one-way. Doubling the voltage roughly doubles the allowable distance.
Materials for this size
Materials for this size
Wire, cable and terminations for 4 AWG.
- THHN/THWN-2 4 AWG copper4 AWG copperBuilding wire in the size this page covers (4 AWG copper).Check price on Amazon →
- NM-B cable 4 AWG4 AWGRomex-type cable for dry indoor branch circuits at this size.Check price on Amazon →
- Wire connectors for 4 AWG4 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.