Quick Reference — 18 AWG
Diameter: 0.0403″ (1.024 mm)
Area: 0.823 mm² (1620 cmil)
Resistance: 6.385 Ω/1000ft (Cu)
Ampacity (75°C): N/AA
Common uses: Low-voltage lighting, doorbells, thermostats, extension cords (light duty)
Wire Properties
| AWG Size | 18 AWG |
| Diameter (inches) | 0.0403″ |
| Diameter (mm) | 1.024 mm |
| Cross-sectional area | 0.823 mm² (1620 circular mils) |
| Resistance — Copper | 6.385 Ω per 1000 ft @ 20°C |
| Resistance — Aluminum | 10.5 Ω per 1000 ft @ 20°C |
| Weight (copper) | ~4.9 lb per 1000 ft |
Ampacity
18 AWG is below the NEC Table 310.16 minimum building wire size (14 AWG). It is not rated for branch circuit wiring in buildings. Used for low-voltage, signal, and electronics applications.
Nearby Sizes for Comparison
| AWG | Dia (in) | Dia (mm) | Area (mm²) | Ω/1000ft Cu | Ampacity 75°C |
|---|---|---|---|---|---|
| 16 | 0.0508 | 1.291 | 1.31 | 4.016 | — |
| 18 | 0.0403 | 1.024 | 0.823 | 6.385 | — |
| 20 | 0.0320 | 0.812 | 0.518 | 10.15 | — |
⚠️ AWG Sizing Reminder
- In AWG, lower numbers = thicker wire. 4 AWG is much thicker than 14 AWG.
- Each 3-gauge decrease doubles the cross-sectional area (e.g., 11 AWG ≈ 2× the area of 14 AWG).
- Each 6-gauge decrease doubles the diameter.
- Always follow local electrical codes — NEC values are minimum requirements.
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