Electrical Box Fill Chart

Electrical boxes have a volume limit so wires are not crammed in. Each conductor counts for a set volume; add them up and the total must fit the box. This chart gives the volume per conductor.

Wire size Volume per conductor
14 AWG 2.00 cu in
12 AWG 2.25 cu in
10 AWG 2.50 cu in
8 AWG 3.00 cu in
How to count: each hot and neutral is one conductor; all grounds together count as one; each device (switch/receptacle) counts as two. Multiply the count by the volume and stay under the box rating.

See the Conduit Fill Chart and How to Wire a Receptacle.

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