NEC Box Fill Calculator (314.16) — Free
Does a receptacle count toward box fill?
Yes. Each device yoke or strap (receptacle or switch) counts as two conductor volume allowances, based on the largest conductor connected to it, per NEC 314.16(B)(4). A device that spans two gangs still counts as two. This is on top of the conductor, clamp, and grounding allowances, so a crowded device box fills up faster than the wire count alone suggests.
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