If standard device boxes are used and all conductors in the box are the same AWG size, which NEC table is permitted to determine the minimum box size?

• A. Table 314.16(A)
• B. Table 314.16(B)
• C. Table 314.28
• D. Table 310.15

Answer: (A)

Box fill must provide enough internal space for all conductors, splices, clamps, and any mounted devices. When you’re using a standard device box and all conductors in the box are the same AWG size, you can use a simplified method to find the minimum box size. That simplified method is Table 314.16(A). It gives a direct minimum cubic-inch requirement based on the number of conductors and devices, accounting for the device yoke, so you don’t have to sum each conductor’s volume individually.

If conductors of different gauges were present, you’d switch to the more general calculation in Table 314.16(B), which tallies volumes by conductor size. The ampacity table (Table 310.15) deals with current-carrying capacity, not the physical space inside a box, and the other table isn’t applicable for this uniform-conductor, standard-box scenario.