8 AWG (American Wire Gauge) wire specifications: 3.2636 mm diameter, 8.3656 mm² area, 50A ampacity (copper, 75°C). Resistance, weight, and common uses.
| Diameter | 3.2636 mm · 0.12849" · 128.49 mils |
| Cross-sectional area | 8.3656 mm² · 16,510 circular mils |
| Resistance (copper, 20°C) | 2.0608 Ω/km · 0.6281 Ω/1000ft |
| Resistance (aluminum, 20°C) | 3.3784 Ω/km · 1.0297 Ω/1000ft |
| Ampacity — copper 60°C | 40 A |
| Ampacity — copper 75°C | 50 A |
| Ampacity — copper 90°C | 55 A |
| Ampacity — aluminum 75°C | 40 A |
| Weight (copper) | 74.955 kg/km · 50.368 lbs/1000ft |
| Weight (aluminum) | 22.587 kg/km · 15.178 lbs/1000ft |
| Closest IEC 60228 size | 10 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 |
8 AWG copper is commonly used for 40–50A circuits such as ranges, cooktops and larger AC condensers. NEC Table 310.16 rates it 50A at 75°C. It measures 3.264 mm in diameter with a 8.37 mm² cross-section.
Per NEC Table 310.16 (30°C ambient, no more than three current-carrying conductors), 8 AWG copper is rated 40A at 60°C, 50A at 75°C and 55A at 90°C. 8 AWG aluminum is rated 35A, 40A and 45A 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. 8 AWG aluminum is rated 40A at 75°C versus 50A for copper, so matching the copper rating takes 6 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.