3 AWG Wire — Amp Rating, Ampacity & Diameter
Ampacity, geometry, resistance, conduit fill and maximum run length for 3 AWG conductors in copper and aluminium.
Quick answer
Copper 75 °C
93A
Aluminium 75 °C
73A
Diameter
0.2294in
Circular mils
52,635
Full specification
| Size designation | 3 AWG |
|---|---|
| AWG gauge number | 3 |
| Circular mils | 52,635 |
| kcmil | 52.63 |
| Bare diameter (in) | 0.2294 |
| Bare diameter (mm) | 5.827 |
| Cross-section (mm²) | 26.67 |
| THHN/THWN-2 OD (in) | 0.352 |
| Insulated area (sq in) | 0.0973 |
| Copper resistance (Ω/1000 ft) | 0.1970 |
| Aluminium resistance (Ω/1000 ft) | 0.3230 |
| Max standard breaker (Cu, 75 °C) | 90 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 | 105 A | 96 A | 86 A | 74 A |
| 6 | 84 A | 77 A | 69 A | 59 A |
| 9 | 74 A | 67 A | 60 A | 52 A |
| 15 | 53 A | 48 A | 43 A | 37 A |
| 25 | 47 A | 43 A | 39 A | 33 A |
Source & method: The governing value is also capped by the termination rating, commonly 75 °C, which for this size is 93 A. Run your own conditions.
Maximum run length at 3% voltage drop
One-way distance for 3 AWG copper before drop exceeds 3%.
| Load | 120 V 1Ø | 240 V 1Ø | 208 V 3Ø | 480 V 3Ø |
|---|---|---|---|---|
| 10 A | 734 ft | 1,468 ft | 1,470 ft | 3,392 ft |
| 15 A | 489 ft | 979 ft | 980 ft | 2,261 ft |
| 20 A | 367 ft | 734 ft | 735 ft | 1,696 ft |
| 30 A | 244 ft | 489 ft | 490 ft | 1,130 ft |
| 40 A | 183 ft | 367 ft | 367 ft | 848 ft |
| 50 A | 146 ft | 293 ft | 294 ft | 678 ft |
How many 3 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 | 3 | 6 | 8 | 13 | 24 | 36 | 47 | 60 |
| IMC | 1 | 1 | 3 | 6 | 9 | 14 | 21 | 32 | 43 | 56 |
| RMC | 1 | 1 | 3 | 6 | 8 | 14 | 19 | 30 | 41 | 52 |
| PVC Sch 40 | 1 | 1 | 3 | 5 | 8 | 13 | 19 | 29 | 40 | 51 |
| PVC Sch 80 | 1 | 1 | 2 | 5 | 7 | 11 | 16 | 26 | 35 | 46 |
3 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 | 79 A | 93 A | 105 A |
| Aluminium | 62 A | 73 A | 82 A |
The 3 AWG copper ampacity figure you use on a real circuit is the 75 °C column, 93 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, 105 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 (73 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 3 AWG with the sizes immediately above and below it before sizing a circuit.
Circuits that use 3 AWG
Breaker ratings whose smallest copper conductor at 75 °C terminations is 3 AWG.
3 AWG amp rating, diameter and metric equivalent
The amp rating for 3 AWG wire depends on the insulation temperature rating, not on the conductor alone. Copper ampacity is about 79 A on a 60 °C conductor, 93 A at 75 °C and 105 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, 3 AWG is 0.2294 in (5.83 mm) in bare diameter, which is 52,635 circular mils. The cross sectional area works out to 26.67 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.
Why 3 AWG is specified so rarely
3 AWG exists in the gauge series and is manufactured, but it is a stocking gap in most supply houses. Designers step from 4 AWG to 2 AWG because the standard overcurrent devices bracket the interval and the cost difference between 3 and 2 is small compared with the risk of a non-stock item delaying a pull.
Where 3 AWG does appear, it is usually on engineered drawings that sized the conductor exactly against a calculated load or a voltage-drop budget rather than rounding to the next stocked size, or as a grounding electrode conductor on a service where the electrode conductor requirement fell between sizes.
The practical takeaway: if a calculation returns 3 AWG, verify local availability before committing, and check whether 2 AWG changes anything downstream. Upsizing costs a little material; it never costs ampacity, though it can change the required conduit trade size and the lug range at both ends.
Frequently asked
- How many amps can 3 AWG wire carry?
- 3 AWG copper is estimated at 79 A at 60 °C, 93 A at 75 °C and 105 A at 90 °C, at 30 °C ambient with no more than three current-carrying conductors. Aluminium of the same size is about 73 A at 75 °C.
- What is the amp rating for 3 gauge wire?
- Use 93 A for 3 AWG copper on equipment with 75 °C terminations, which covers most breakers and panel lugs. Read 79 A instead when the conductor is inside NM-B cable, and treat 105 A as the derating base only. Aluminium of the same size is about 73 A at 75 °C.
- What breaker size goes with 3 AWG copper?
- The largest standard overcurrent device that 3 AWG copper supports at 75 °C is 90 A. For a continuous load, the load itself must not exceed 80% of that rating.
- What is the diameter of 3 AWG wire?
- The bare conductor is 0.2294 inches (5.827 mm) in diameter, which is 52,635 circular mils. With THHN/THWN-2 insulation the nominal outside diameter is about 0.352 inches.
- What is the resistance of 3 AWG wire?
- About 0.1970 ohms per 1000 feet for copper and 0.3230 ohms per 1000 feet for aluminium, at 75 °C.
- How far can I run 3 AWG wire?
- Distance depends on load and voltage. At 20 A on a 120 V single-phase circuit, 3 AWG copper stays under 3% voltage drop for about 367 feet one-way. Doubling the voltage roughly doubles the allowable distance.
Related charts & calculators
- Nut Size ChartBolt size to hex nut across-flats wrench size, SAE and metric.
- Allen Wrench Size ChartHex key sizes with SAE and metric cross-reference.
- 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.