Junction Box Fill Calculator

Calculate minimum junction box volume per NEC 314.16. Add all conductors, devices, clamps, and fittings to find the correct box size.

NEC 314.16: Each conductor counts as one unit based on its size. Devices count as 2 units, equipment grounds count as 1 unit total (largest conductor size), and internal cable clamps count as 1 unit.
Quick add – common cable types
Conductors and fittings
Item description AWG size Qty
+ Add conductor / item
Grounding conductors
All grounds = 1 unit (largest size)

Please add at least one conductor.

Minimum box volume required
0 cu in
Volume breakdown
NEC Table 314.16(A) – Standard box volumes
Box type Volume Max 14 AWG
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