NEC Box Fill Calculator (314.16) — Free
How many wires can I put in a single-gang box?
It depends on the box’s cubic-inch volume and wire size. A common 18 cu in single-gang box allows eight 14 AWG conductors before any device or clamp deductions — but a switch or receptacle (a two-conductor allowance) plus the ground reduce that to about five incoming circuit conductors. Always calculate from the box’s marked volume, not a fixed wire count.
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