Calculate required box volume according to NEC 314.16(B) standards.
Conductor Details
Grounding Wires?
Internal Cable Clamps?
Required Volume
Enter conductor details for fill analysis
About this calculator
Overview
To prevent electrical fires and ensure safety, the National Electrical Code (NEC) limits the number of wires and devices in an electrical box. This calculator helps you determine the minimum box size needed in cubic inches.
💡
Pro Tips
Always use the largest wire size in the box to determine the volume allowance for clamps and grounding.
If you're struggling to fit wires in, consider using a deeper '4-square' box with a single-gang industrial cover.
A conductor loop that is 12 inches or longer counts twice.
!
Fun Facts
"Wait, all grounding wires in a box only count as ONE volume allowance, regardless of how many there are!"
"Devices like switches and receptacles count as DOUBLE the volume of the largest wire connected to them."
"If you use a 'mud ring' or extension, you can add its marked volume to the total capacity of the box."
