3 AWG (American Wire Gauge) wire specifications: 5.8273 mm diameter, 26.6705 mm² area, 100A ampacity (copper, 75°C). Resistance, weight, and common uses.
| Diameter | 5.8273 mm · 0.229423" · 229.42 mils |
| Cross-sectional area | 26.6705 mm² · 52,635 circular mils |
| Resistance (copper, 20°C) | 0.6464 Ω/km · 0.197 Ω/1000ft |
| Resistance (aluminum, 20°C) | 1.0597 Ω/km · 0.323 Ω/1000ft |
| Ampacity — copper 60°C | 85 A |
| Ampacity — copper 75°C | 100 A |
| Ampacity — copper 90°C | 115 A |
| Ampacity — aluminum 75°C | 75 A |
| Weight (copper) | 238.967 kg/km · 160.578 lbs/1000ft |
| Weight (aluminum) | 72.01 kg/km · 48.389 lbs/1000ft |
| Closest IEC 60228 size | 25 mm² |
| Skin depth at 60 Hz | 8.531 mm |
| Type | Temperature | Description |
|---|---|---|
| THHN/THWN-2 | 90°C dry / 75°C wet | Most common for building wire |
| XHHW-2 | 90°C dry and wet | Cross-linked polyethylene, moisture resistant |
| USE-2 | 90°C | Underground service entrance |
| NM-B (Romex) | 90°C | Non-metallic sheathed cable for residential |
| UF-B | 60°C | Underground feeder, direct burial |
3 AWG copper is commonly used for 70–80A subpanel feeders. NEC Table 310.16 rates it 100A at 75°C. It measures 5.827 mm in diameter with a 26.7 mm² cross-section.
Per NEC Table 310.16 (30°C ambient, no more than three current-carrying conductors), 3 AWG copper is rated 85A at 60°C, 100A at 75°C and 115A at 90°C. 3 AWG aluminum is rated 65A, 75A and 85A in the same columns. On circuits of 100A or less, NEC 110.14(C) generally requires the 60°C column unless every termination is rated 75°C.
Yes. 3 AWG aluminum is rated 75A at 75°C versus 100A for copper, so matching the copper rating takes 1 AWG aluminum. Aluminum at this size is common for feeders, subpanels and service conductors (SER, USE-2, XHHW-2). Use AL-rated lugs, torque to the manufacturer’s spec and apply antioxidant compound where required.