How Many Amps Can 12 AWG Copper Wire Handle?
Verified against NEC 2023, checked against the 2026 edition · Last checked August 19, 2026
12 AWG copper wire carries 20 A at 60°C, 25 A at 75°C and 30 A at 90°C · Table 310.16. Which column applies depends on the termination rating · 110.14(C). NM-B cable always uses the 60°C column · 334.80. No matter the column, the breaker on 12 AWG copper tops out at 20 A · 240.4(D).
Common on this size: 20 A receptacle and small appliance circuits.
| Column · insulation examples | Ampacity | Basis |
|---|---|---|
| 60°C · TW, UF | 20 A | Table 310.16 |
| 75°C · THW, THWN, XHHW wet, USE | 25 A | Table 310.16 |
| 90°C · THHN, THWN-2, XHHW-2 | 30 A | Table 310.16 |
| Maximum breaker | 20 A | 240.4(D) |
THHW and XHHW are 90°C only in dry and damp locations; wet locations put them in the 75°C column. XHHW-2 and THWN-2 hold 90°C wet or dry · Table 310.4(1).
| Current-carrying conductors | Percent of table ampacity |
|---|---|
| 4 to 6 | 80% |
| 7 to 9 | 70% |
| 10 to 20 | 50% |
| 21 to 30 | 45% |
| 31 to 40 | 40% |
| 41 and more | 35% |
Ambient above 86°F applies a further correction from the band table of 310.15(B)(1). The free wire size calculator applies both automatically.
Derate it in seconds, offline.
The JobVolt app applies ambient correction, conductor adjustment and termination limits to 12 AWG copper with every step cited, then exports inspector-ready PDF submittals.
Common questions
- How many amps can 12 gauge copper wire handle?
- 20 A at 60°C terminations, 25 A at 75°C and 30 A at 90°C, per NEC Table 310.16 with no more than three current-carrying conductors at 86°F ambient. The overcurrent device still caps at 20 A · 240.4(D).
- What size breaker goes on 12 AWG copper?
- 20 A is the maximum · 240.4(D). Larger breakers are not permitted on 12 AWG copper outside specific rules like motor circuits · 240.4(G).
- Why does the chart say 30 A for 12 AWG copper but the breaker only 20 A?
- 30 A is the 90°C table ampacity, the starting point for derating. The small-conductor rule caps the overcurrent device separately · 240.4(D). Both are true at once.
- Does conduit fill change the ampacity of 12 AWG copper?
- Four or more current-carrying conductors in one raceway derate the table value · 310.15(C)(1). At 4 to 6 conductors, 12 AWG copper starts from 80% of the 90°C cell: 24 A before any further correction. Heat above 86°F derates it further · 310.15(B)(1).