18
18 AWG Wire Box Fill
18 AWG conductors are typically used for low-voltage applications and control wiring.
1.5
cu.in. per conductor
24.6
mm3 per conductor
7A
Max Ampacity
Common Applications
Thermostat wiring
Doorbell circuits
Low-voltage controls
Box Capacity 18 AWG
Maximum number of conductors that fit in common electrical boxes (conductors only, not accounting for devices, clamps, or grounds).
| Box Type | Volume | Max 18 AWG* |
|---|---|---|
| 4" Square x 1-1/4" Deep | 18 cu.in. | 12 |
| 4" Square x 1-1/2" Deep | 21 cu.in. | 14 |
| 4" Square x 2-1/8" Deep | 30.3 cu.in. | 20 |
| 4-11/16" Square x 1-1/4" Deep | 25.5 cu.in. | 17 |
| 4-11/16" Square x 1-1/2" Deep | 29.5 cu.in. | 19 |
| 4-11/16" Square x 2-1/8" Deep | 42 cu.in. | 28 |
| Octagon Box 1-1/2" Deep | 15.5 cu.in. | 10 |
| 4" Octagon Box 1-1/2" Deep | 15.5 cu.in. | 10 |
| Octagon Box 2-1/8" Deep | 21.5 cu.in. | 14 |
| Single Gang Device Box 2-3/4" Deep | 14 cu.in. | 9 |
| Single Gang Device Box 18 cu.in. | 18 cu.in. | 12 |
| Single Gang Device Box 3-1/2" Deep | 18 cu.in. | 12 |