NEC 2023
Table 314.16(A) — Standard Metal Box Volumes
Interior cubic-inch volumes for standard metal outlet boxes. Use these values when verifying box fill per NEC Section 314.16.
| Box Description | Volume (in³) |
|---|---|
| 4×1-1/4 square | 18.0 |
| 4×1-1/2 square | 21.0 |
| 4×2-1/8 square | 30.3 |
| 4×4×1-1/2 square(4-11/16 in. square) | 42.0 |
| 3×2×2 device | 10.5 |
| 3×2×2-1/4 device | 12.5 |
| 3×2×2-1/2 device | 14.0 |
| 3×2×2-3/4 device | 15.5 |
| 3×2×3-1/2 device | 18.0 |
Table 314.16(B)(1) — Volume per Conductor
Each conductor that enters the box counts as one volume allowance. Conductors that originate and terminate inside the box do not add additional volume.
| Conductor Size | Volume per Conductor (in³) |
|---|---|
| #18 AWG | 1.50 |
| #16 AWG | 1.75 |
| #14 AWG | 2.00 |
| #12 AWG | 2.25 |
| #10 AWG | 2.50 |
| #8 AWG | 3.00 |
| #6 AWG | 5.00 |
Reference: NEC 2023 Section 314.16, Table 314.16(A) and Table 314.16(B)(1). Clamps, support fittings, and devices each require additional volume allowances per 314.16(B)(2)–(5). Listed nonmetallic boxes are marked with their cubic-inch volume.