Electrical Box Fill Calculator

Calculate the minimum electrical box size per NEC 314.16 based on conductor count, grounds, clamps, and devices.

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Largest Wire Gauge

Volume is based on the largest conductor in the box per NEC 314.16

Current-Carrying Conductors

Count each hot and neutral wire — not grounds

Ground Wires

All grounds count as 1 per NEC 314.16(B)(5)

Internal Cable Clamps

External clamps don't count — only internal

Devices (Switches/Receptacles)

Each yoke/strap counts as 2× volume

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