Construction
Outlet Box Fill Calculator
Every wire, device, clamp, and ground in a box has a volume allowance. Overstuff and the box must be replaced.
Fill (cu in)
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- Box capacity
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- Margin
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- OK?
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FAQ
Why count devices as 2 wires? +
NEC 314.16(B)(4): each yoke counts as 2 conductors of largest wire connected to it.
All grounds count as one? +
Yes — all equipment grounding conductors collectively count as a single conductor (314.16(B)(5)).