12 AWG Wire — Ampacity, Conduit Fill & Dimensions
Everything the code tables say about 12 AWG conductors on one page: ampacity by temperature rating, breaker limits, conduit fill, physical size, resistance and voltage-drop distances.
12 AWG copper carries 20 A at 60°C, 25 A at 75°C and 30 A at 90°C. Overcurrent protection is capped at 20 A for copper and 15 A for aluminum by the small-conductor rule in 240.4(D), whatever the ampacity column says.
12 AWG ampacity
| Copper | Aluminum | |||||
|---|---|---|---|---|---|---|
| Installation | 60°C | 75°C | 90°C | 60°C | 75°C | 90°C |
| Raceway, cable or earth — Table 310.16 | 20 | 25 | 30 | 15 | 20 | 25 |
| Single conductor in free air — Table 310.17 | 30 | 35 | 40 | 25 | 30 | 35 |
Typical use: 20 A circuits: kitchen, bathroom, laundry and garage receptacles, and most commercial branch circuits.
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, 12 AWG is the minimum for circuits protected at up to 20 A; in aluminum, up to 15 A. See the grounding conductor table.
12 AWG conduit fill
| Conduit | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 4" |
|---|---|---|---|---|---|---|---|---|---|
| EMT | 9 | 16 | 26 | 45 | 61 | 101 | 176 | 266 | 443 |
| PVC Schedule 40 | 8 | 15 | 25 | 43 | 59 | 99 | 141 | 218 | 377 |
| PVC Schedule 80 | 6 | 12 | 20 | 37 | 51 | 86 | 124 | 193 | 338 |
| Rigid Metal Conduit | 9 | 16 | 26 | 46 | 62 | 102 | 146 | 225 | 387 |
| IMC | 10 | 17 | 29 | 49 | 67 | 109 | 154 | 238 | 410 |
| Flexible Metal Conduit | 9 | 16 | 24 | 38 | 56 | 98 | 147 | 212 | 378 |
| Liquidtight Flexible Metal Conduit | 9 | 16 | 26 | 46 | 59 | 97 | 146 | 225 | 381 |
| ENT | 8 | 15 | 25 | 43 | 59 | 99 | — | — | — |
Mixing sizes or using another insulation? Use the conduit fill calculator.
12 AWG dimensions
| Insulation | Diameter (in) | Diameter (mm) | Area (in²) | Area (mm²) |
|---|---|---|---|---|
| THHN, THWN, THWN-2 | 0.130 | 3.30 | 0.0133 | 8.6 |
| XHHW, XHHW-2, XHH | 0.152 | 3.86 | 0.0181 | 11.7 |
| TW, THW, THHW, THW-2 | 0.152 | 3.86 | 0.0181 | 11.7 |
| RHH, RHW, RHW-2 (with outer covering) | 0.212 | 5.38 | 0.0353 | 22.8 |
12 AWG voltage drop
| Load | 120 V 1-phase | 240 V 1-phase | 208 V 3-phase | 480 V 3-phase |
|---|---|---|---|---|
| 5 A | 181 ft | 363 ft | 363 ft | 839 ft |
| 10 A | 90 ft | 181 ft | 181 ft | 419 ft |
| 15 A | 60 ft | 121 ft | 121 ft | 279 ft |
| 20 A | 45 ft | 90 ft | 90 ft | 209 ft |
Based on 1.98 Ω per 1000 ft for stranded copper at 75°C (3.25 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 12 AWG wire carry?
12 AWG copper is rated 20 A at 60°C, 25 A at 75°C and 30 A at 90°C when run in conduit or cable. Aluminum is rated 15, 20 and 25 A. Breaker size is limited to 20 A for copper.
What size conduit do I need for 12 AWG wire?
Three 12 AWG THHN conductors need at least 1/2-inch EMT. 1/2-inch EMT holds 9 and 3/4-inch holds 16.
What is the diameter of 12 AWG wire?
The bare conductor is 6,530 circular mils (3.31 mm²). With THHN insulation the overall diameter is about 0.130 in (3.30 mm) and the area is 0.0133 in², which is the figure used for conduit fill.
How far can I run 12 AWG wire?
For a 3% voltage drop on a 240 V single-phase circuit carrying 20 A, about 90 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.