4 AWG Wire — Ampacity, Conduit Fill & Dimensions
Everything the code tables say about 4 AWG conductors on one page: ampacity by temperature rating, breaker limits, conduit fill, physical size, resistance and voltage-drop distances.
4 AWG copper carries 70 A at 60°C, 85 A at 75°C and 95 A at 90°C.
4 AWG ampacity
| Copper | Aluminum | |||||
|---|---|---|---|---|---|---|
| Installation | 60°C | 75°C | 90°C | 60°C | 75°C | 90°C |
| Raceway, cable or earth — Table 310.16 | 70 | 85 | 95 | 55 | 65 | 75 |
| Single conductor in free air — Table 310.17 | 105 | 125 | 140 | 80 | 100 | 115 |
Typical use: 70–85 A feeders. In copper it is also the 100 A dwelling-service size under the 83% rule of 310.12.
Use the column that matches the lowest temperature rating in the circuit — usually the 75°C terminations on breakers and lugs. The 90°C column is a starting point for derating, not a rating you can load the wire to. NM-B (Romex) cable is always limited to the 60°C column.
As a copper equipment grounding conductor, 4 AWG is the minimum for circuits protected at up to 300 A; in aluminum, up to 200 A. See the grounding conductor table.
4 AWG conduit fill
| Conduit | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 4" |
|---|---|---|---|---|---|---|---|---|---|
| EMT | 1 | 2 | 4 | 7 | 10 | 16 | 28 | 43 | 71 |
| PVC Schedule 40 | 1 | 1 | 4 | 7 | 9 | 16 | 22 | 35 | 61 |
| PVC Schedule 80 | 1 | 1 | 3 | 6 | 8 | 14 | 20 | 31 | 54 |
| Rigid Metal Conduit | 1 | 2 | 4 | 7 | 10 | 16 | 23 | 36 | 62 |
| IMC | 1 | 3 | 4 | 8 | 11 | 17 | 25 | 38 | 66 |
| Flexible Metal Conduit | 1 | 2 | 4 | 6 | 9 | 16 | 24 | 34 | 61 |
| Liquidtight Flexible Metal Conduit | 1 | 2 | 4 | 7 | 9 | 15 | 23 | 36 | 61 |
| ENT | 1 | 1 | 4 | 7 | 9 | 16 | — | — | — |
Mixing sizes or using another insulation? Use the conduit fill calculator.
4 AWG dimensions
| Insulation | Diameter (in) | Diameter (mm) | Area (in²) | Area (mm²) |
|---|---|---|---|---|
| THHN, THWN, THWN-2 | 0.324 | 8.23 | 0.0824 | 53.2 |
| XHHW, XHHW-2, XHH | 0.322 | 8.18 | 0.0814 | 52.5 |
| TW, THW, THHW, THW-2 | 0.352 | 8.94 | 0.0973 | 62.8 |
| RHH, RHW, RHW-2 (with outer covering) | 0.412 | 10.46 | 0.1333 | 86.0 |
4 AWG voltage drop
| Load | 120 V 1-phase | 240 V 1-phase | 208 V 3-phase | 480 V 3-phase |
|---|---|---|---|---|
| 30 A | 194 ft | 389 ft | 389 ft | 899 ft |
| 40 A | 146 ft | 292 ft | 292 ft | 674 ft |
| 50 A | 116 ft | 233 ft | 233 ft | 539 ft |
| 60 A | 97 ft | 194 ft | 194 ft | 449 ft |
| 80 A | 73 ft | 146 ft | 146 ft | 337 ft |
Based on 0.308 Ω per 1000 ft for stranded copper at 75°C (0.508 Ω for aluminum). For other loads and lengths use the voltage drop calculator.
All wire sizes
- 14 AWG
- 12 AWG
- 10 AWG
- 8 AWG
- 6 AWG
- 4 AWG
- 3 AWG
- 2 AWG
- 1 AWG
- 1/0 AWG
- 2/0 AWG
- 3/0 AWG
- 4/0 AWG
- 250 kcmil
- 300 kcmil
- 350 kcmil
- 400 kcmil
- 500 kcmil
- 600 kcmil
- 700 kcmil
- 750 kcmil
- 800 kcmil
- 900 kcmil
- 1000 kcmil
Frequently asked questions
How many amps can 4 AWG wire carry?
4 AWG copper is rated 70 A at 60°C, 85 A at 75°C and 95 A at 90°C when run in conduit or cable. Aluminum is rated 55, 65 and 75 A. Most terminations are rated 75°C, so the 75°C figure is the one normally used.
What size conduit do I need for 4 AWG wire?
Three 4 AWG THHN conductors need at least 1-inch EMT. Add the ground wire’s area and check the chart above for larger bundles.
What is the diameter of 4 AWG wire?
The bare conductor is 41,740 circular mils (21.15 mm²). With THHN insulation the overall diameter is about 0.324 in (8.23 mm) and the area is 0.0824 in², which is the figure used for conduit fill.
How far can I run 4 AWG wire?
For a 3% voltage drop on a 240 V single-phase circuit carrying 80 A, about 146 feet one way in copper. Halve that at 120 V. Lighter loads go proportionally farther.
NECTables.com is an independent reference and is not affiliated with, endorsed by, or a substitute for the National Fire Protection Association (NFPA). NEC® and National Electrical Code® are registered trademarks of the NFPA. Values shown are commonly published engineering data and independent calculations based on the methods of NFPA 70; they are not a reproduction of the Code. Always confirm against the edition adopted in your jurisdiction, including local amendments, and consult a licensed electrician or engineer before doing electrical work.