Wire Gauge Box Fill Reference
Find conductor volume allowances by AWG size for NEC 314.16 box fill calculations. Select a wire gauge for detailed information and box fill calculations.
AWG
Volume: 1.5 cu.in.
Max Amps: 7A
18 AWG conductors are typically used for low-voltage applications and control wiring.
AWG
Volume: 1.75 cu.in.
Max Amps: 10A
16 AWG conductors are used for light-duty circuits and appliance cords.
AWG
Volume: 2 cu.in.
Max Amps: 15A
14 AWG is the minimum size for standard 15-amp household circuits per NEC.
AWG
Volume: 2.25 cu.in.
Max Amps: 20A
12 AWG conductors are required for 20-amp circuits and kitchen/bathroom outlets.
AWG
Volume: 2.5 cu.in.
Max Amps: 30A
10 AWG conductors are used for 30-amp circuits such as dryers and water heaters.
AWG
Volume: 3 cu.in.
Max Amps: 40A
8 AWG conductors support 40-amp circuits for ranges and large appliances.
AWG
Volume: 5 cu.in.
Max Amps: 55A
6 AWG conductors are used for 55-amp circuits and sub-panel feeders.
NEC Table 314.16(B) Quick Reference
| AWG | Volume (cu.in.) | Volume (mm³) | Ampacity | Common Uses |
|---|---|---|---|---|
| 18 AWG | 1.5 | 24.6 | 7A | Thermostat wiring, Doorbell circuits |
| 16 AWG | 1.75 | 28.7 | 10A | Extension cords, Light fixtures |
| 14 AWG | 2 | 32.8 | 15A | 15-amp circuits, Lighting circuits |
| 12 AWG | 2.25 | 36.9 | 20A | 20-amp circuits, Kitchen outlets |
| 10 AWG | 2.5 | 41 | 30A | 30-amp circuits, Electric dryers |
| 8 AWG | 3 | 49.2 | 40A | 40-amp circuits, Electric ranges |
| 6 AWG | 5 | 82 | 55A | 55-amp circuits, Sub-panel feeders |
Understanding Wire Gauge for Box Fill
The American Wire Gauge (AWG) system determines the volume each conductor occupies in an electrical box. Larger conductors (smaller AWG numbers) require more space per NEC 314.16.
How Wire Gauge Affects Box Fill
Each conductor entering an electrical box requires a specific volume allowance based on its AWG size. For example:
- A 14 AWG conductor requires 2.00 cubic inches
- A 12 AWG conductor requires 2.25 cubic inches
- A 6 AWG conductor requires 5.00 cubic inches
Calculate Your Box Fill
Use our free box fill calculator to automatically calculate fill requirements based on your conductor sizes and quantities.