4/0 AWG Wire — Amp Rating, Ampacity & Diameter
Ampacity, geometry, resistance, conduit fill and maximum run length for 4/0 AWG conductors in copper and aluminium.
Quick answer
Copper 75 °C
230A
Aluminium 75 °C
180A
Diameter
0.4600in
Circular mils
211,600
Full specification
| Size designation | 4/0 AWG |
|---|---|
| AWG gauge number | 4/0 |
| Circular mils | 211,600 |
| kcmil | 211.60 |
| Bare diameter (in) | 0.4600 |
| Bare diameter (mm) | 11.684 |
| Cross-section (mm²) | 107.22 |
| THHN/THWN-2 OD (in) | 0.642 |
| Insulated area (sq in) | 0.3237 |
| Copper resistance (Ω/1000 ft) | 0.0490 |
| Aluminium resistance (Ω/1000 ft) | 0.0803 |
| Max standard breaker (Cu, 75 °C) | 225 A |
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 | 260 A | 237 A | 212 A | 184 A |
| 6 | 208 A | 190 A | 170 A | 147 A |
| 9 | 182 A | 166 A | 149 A | 129 A |
| 15 | 130 A | 119 A | 106 A | 92 A |
| 25 | 117 A | 107 A | 95 A | 83 A |
Source & method: The governing value is also capped by the termination rating, commonly 75 °C, which for this size is 230 A. Run your own conditions.
Maximum run length at 3% voltage drop
One-way distance for 4/0 AWG copper before drop exceeds 3%.
| Load | 120 V 1Ø | 240 V 1Ø | 208 V 3Ø | 480 V 3Ø |
|---|---|---|---|---|
| 10 A | 2,952 ft | 5,905 ft | 5,909 ft | 13,637 ft |
| 15 A | 1,968 ft | 3,936 ft | 3,939 ft | 9,091 ft |
| 20 A | 1,476 ft | 2,952 ft | 2,954 ft | 6,818 ft |
| 30 A | 984 ft | 1,968 ft | 1,969 ft | 4,545 ft |
| 40 A | 738 ft | 1,476 ft | 1,477 ft | 3,409 ft |
| 50 A | 590 ft | 1,181 ft | 1,181 ft | 2,727 ft |
How many 4/0 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 | 1 | 1 | 4 | 7 | 10 | 14 | 18 |
| IMC | — | — | 1 | 1 | 2 | 4 | 6 | 9 | 13 | 16 |
| RMC | — | — | 1 | 1 | 1 | 4 | 6 | 9 | 12 | 15 |
| PVC Sch 40 | — | — | 1 | 1 | 1 | 4 | 5 | 8 | 12 | 15 |
| PVC Sch 80 | — | — | 1 | 1 | 1 | 3 | 5 | 7 | 10 | 13 |
4/0 AWG copper ampacity vs aluminium ampacity
Ampacity by conductor material and insulation temperature rating, at 30 °C ambient with no more than three current-carrying conductors.
| Material | 60 °C (TW, NM-B) | 75 °C (THW, THWN, XHHW) | 90 °C (THHN, THWN-2, XHHW-2) |
|---|---|---|---|
| Copper | 195 A | 230 A | 260 A |
| Aluminium | 152 A | 180 A | 202 A |
The 4/0 AWG copper ampacity figure you use on a real circuit is the 75 °C column, 230 A, because breakers and lugs on most equipment are listed for 75 °C even when the conductor insulation is rated 90 °C. The 90 °C value, 260 A, is the starting point for ambient and conductor-count derating only — you derate from 90 °C, then cap the answer at the termination rating.
Aluminium of the same size carries roughly 78% of the copper value (180 A at 75 °C), so an aluminium feeder is normally stepped up one to two sizes to match a copper circuit. NM-B cable is always read from the 60 °C column regardless of the temperature stamped on the conductor insulation.
Source & method: Values are model estimates from conductor geometry and resistivity — see methodology and verify against the NEC edition enforced locally.
Neighbouring sizes
Compare 4/0 AWG with the sizes immediately above and below it before sizing a circuit.
Circuits that use 4/0 AWG
Breaker ratings whose smallest copper conductor at 75 °C terminations is 4/0 AWG.
4/0 AWG amp rating, diameter and metric equivalent
The amp rating for 4/0 AWG wire depends on the insulation temperature rating, not on the conductor alone. Copper ampacity is about 195 A on a 60 °C conductor, 230 A at 75 °C and 260 A at 90 °C, all at 30 °C ambient with no more than three current-carrying conductors in the raceway. The carrying capacity drops from there in hot spaces or crowded conduit, and terminations rated 75 °C cap what you can actually use.
Geometrically, 4/0 AWG is 0.4600 in (11.68 mm) in bare diameter, which is 211,600 circular mils. The cross sectional area works out to 107.22 mm², so the nearest IEC 60228 metric conductor is the next standard size at or above that figure — AWG sizes and mm² sizes never line up exactly, so round up rather than to the closest value.
American Wire Gauge (AWG) is a standard specification for the sizes of solid round wires used as electrical conductors, and the AWG number counts the drawing operations used to reach the diameter. That is why larger gauges are thinner wire and why standardized wire steps follow a fixed ratio: one AWG step changes diameter by about 12.2% and area by about 26%. Above 1 AWG the American standard continues 1/0 to 4/0, then switches to kcmil for anything larger.
Where 4/0 actually gets used
4/0 is the single most recognisable large conductor in North American residential work: 4/0 aluminium is the standard 200 A dwelling service and main-feeder conductor under the service allowance, and 4/0 copper serves roughly 230 A feeders in commercial installations.
It is the largest size most electricians will terminate on a routine basis without engineered hardware. Meter bases, 200 A load centres and service disconnects are typically listed with lugs that accept 4/0 aluminium directly, which is why the size persists even where a calculation would allow something smaller.
Above 4/0 the gauge series ends and sizing moves to thousands of circular mils, so 4/0 is also the practical boundary between ordinary building wiring and engineered distribution. Beyond it, parallel sets, cable tray, busway and larger raceway all become normal design options rather than exceptions.
Frequently asked
- How many amps can 4/0 AWG wire carry?
- 4/0 AWG copper is estimated at 195 A at 60 °C, 230 A at 75 °C and 260 A at 90 °C, at 30 °C ambient with no more than three current-carrying conductors. Aluminium of the same size is about 180 A at 75 °C.
- What is the amp rating for 4/0 gauge wire?
- Use 230 A for 4/0 AWG copper on equipment with 75 °C terminations, which covers most breakers and panel lugs. Read 195 A instead when the conductor is inside NM-B cable, and treat 260 A as the derating base only. Aluminium of the same size is about 180 A at 75 °C.
- What breaker size goes with 4/0 AWG copper?
- The largest standard overcurrent device that 4/0 AWG copper supports at 75 °C is 225 A. For a continuous load, the load itself must not exceed 80% of that rating.
- What is the diameter of 4/0 AWG wire?
- The bare conductor is 0.4600 inches (11.684 mm) in diameter, which is 211,600 circular mils. With THHN/THWN-2 insulation the nominal outside diameter is about 0.642 inches.
- What is the resistance of 4/0 AWG wire?
- About 0.0490 ohms per 1000 feet for copper and 0.0803 ohms per 1000 feet for aluminium, at 75 °C.
- How far can I run 4/0 AWG wire?
- Distance depends on load and voltage. At 20 A on a 120 V single-phase circuit, 4/0 AWG copper stays under 3% voltage drop for about 1476 feet one-way. Doubling the voltage roughly doubles the allowable distance.
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