12 AWG (American Wire Gauge) wire specifications: 2.0525 mm diameter, 3.3088 mm² area, 25A ampacity (copper, 75°C), protected at 20A max per NEC 240.4(D). Resistance, weight, and common uses.
| Diameter | 2.0525 mm · 0.080808" · 80.81 mils |
| Cross-sectional area | 3.3088 mm² · 6,530 circular mils |
| Resistance (copper, 20°C) | 5.2104 Ω/km · 1.5881 Ω/1000ft |
| Resistance (aluminum, 20°C) | 8.5417 Ω/km · 2.6035 Ω/1000ft |
| Ampacity — copper 60°C | 20 A |
| Ampacity — copper 75°C | 25 A |
| Ampacity — copper 90°C | 30 A |
| Ampacity — aluminum 75°C | 20 A |
| Weight (copper) | 29.647 kg/km · 19.922 lbs/1000ft |
| Weight (aluminum) | 8.934 kg/km · 6.003 lbs/1000ft |
| Closest IEC 60228 size | 4 mm² |
| Skin depth at 60 Hz | 8.531 mm |
| Type | Temperature | Description |
|---|---|---|
| THHN/THWN-2 | 90°C dry / 75°C wet | Building wire |
| NM-B (Romex) | 90°C | Residential cable |
| MTW | 60/90°C | Machine tool wire |
| TFFN | 90°C | Fixture wire |
12 AWG copper is commonly used for 20A receptacle circuits, including kitchen, bathroom and garage outlets. NEC Table 310.16 rates it 25A at 75°C, but NEC 240.4(D) limits the breaker or fuse protecting it to 20A, which is why it is the standard wire for 20A circuits. It measures 2.053 mm in diameter with a 3.31 mm² cross-section.
Per NEC Table 310.16 (30°C ambient, no more than three current-carrying conductors), 12 AWG copper is rated 20A at 60°C, 25A at 75°C and 30A at 90°C. 12 AWG aluminum is rated 15A, 20A and 25A in the same columns. Regardless of those ratings, NEC 240.4(D) caps overcurrent protection at 20A for copper and 15A for aluminum. On circuits of 100A or less, NEC 110.14(C) generally requires the 60°C column unless every termination is rated 75°C.
Yes, but it is uncommon for new work. 12 AWG aluminum is rated 20A at 75°C, and NEC 240.4(D) limits it to a 15A breaker. Small-gauge aluminum branch wiring from the 1960s–70s is known for overheating at connections, so any device on it must be rated CO/ALR or AL/CU, or pigtailed with approved connectors.