18 AWG (American Wire Gauge) wire specifications: 1.0237 mm diameter, 0.823 mm² area, 14A ampacity (copper, 90°C column only). Resistance, weight, and common uses.
| Diameter | 1.0237 mm · 0.040303" · 40.3 mils |
| Cross-sectional area | 0.823 mm² · 1,624 circular mils |
| Resistance (copper, 20°C) | 20.9466 Ω/km · 6.3845 Ω/1000ft |
| Resistance (aluminum, 20°C) | 34.3388 Ω/km · 10.4665 Ω/1000ft |
| Ampacity — copper 60°C | — A |
| Ampacity — copper 75°C | — A |
| Ampacity — copper 90°C | 14 A |
| Flexible cord (NEC Table 400.5(A)(1)) | 10 A (2 conductors) · 7 A (3 conductors) |
| Ampacity — aluminum 75°C | — A |
| Weight (copper) | 7.374 kg/km · 4.955 lbs/1000ft |
| Weight (aluminum) | 2.222 kg/km · 1.493 lbs/1000ft |
| Closest IEC 60228 size | 0.75 mm² |
| Skin depth at 60 Hz | 8.531 mm |
| Type | Temperature | Description |
|---|---|---|
| TFFN/TFN | 90°C | Fixture wire |
| SPT-2 | 60–105°C | Lamp and zip cord |
| SJT/SJOOW | 60–105°C | Portable and extension cord |
| MTW | 60/90°C | Machine tool wire |
18 AWG copper is used for lamp cords, fixture wires, thermostats and control circuits. It is too small for general-purpose branch circuits, which require at least 14 AWG copper. Diameter is 1.024 mm and cross-section 0.823 mm².
NEC Table 310.16 lists 18 AWG only in the 90°C column, at 14A. As flexible cord, NEC Table 400.5(A)(1) rates it 10A with two current-carrying conductors or 7A with three. NEC 240.4(D) permits 18 AWG on 7A overcurrent protection only in specific cases such as listed fixture wire and cords.