Method for Measuring Junction Box Capacity

Use this junction box sizing calculator to size your electrical enclosures. Enter wire gauges for box fill or select conduit trade sizes for pull box sizing. The first step is to determine the total number of conductor equivalents in the box. Determine the proper junction box size for your electrical installation by calculating volume requirements, fill percentages, and ensuring compliance with electrical codes and safety. An electrical junction box is a protective container where electrical connections, known as splices, are housed or where wiring devices like switches and outlets are installed. [pdf]