Conduit Fill Calculator

This calculator helps determine the appropriate conduit size based on the number and type of cables you need to run. The primary principle is based on the National Electrical Code (NEC), which generally stipulates that for three or more cables in a conduit, the cross-sectional area of all cables should not exceed 40% of the conduit's internal cross-sectional area.

• Cable Areas: The calculator uses the Outer Diameter (OD) of each cable type to calculate its circular area (Area = π * (OD/2)²). The total area for each cable type is its area multiplied by the quantity.
• Total Cable Area: All individual cable areas are summed up to get a grand total area for all cables.
• Conduit Sizing: The calculator then checks standard conduit trade sizes. It finds the smallest conduit where the total cable area is less than or equal to 40% of that conduit's internal area.
• Alternative Sizing: An alternative calculation is provided for scenarios where a maximum conduit size (e.g., 1-1/4") is preferred, potentially requiring multiple conduits.

The reference tables for conduit sizes and cable characteristics provide the underlying data used in these calculations. You can also add custom cables if your specific type isn't listed.