Conduit Fill Calculator — Free Online Calculator
Calculate conduit fill per NEC Chapter 9. Enter wire count and gauge to find the minimum conduit trade size for EMT, PVC, and rigid conduit.
How to Use This Calculator
Select the wire gauge, enter the number of conductors, choose insulation type and conduit type. The calculator determines the minimum conduit trade size per NEC Chapter 9 fill tables.
The Formula Explained
NEC Chapter 9 Table 1 sets maximum conduit fill: 53% for 1 wire, 31% for 2 wires, 40% for 3 or more. The calculator sums the individual wire cross-sectional areas (from NEC Chapter 9 Table 5) and divides by the fill percentage to find the minimum conduit area needed, then selects the smallest trade size that meets or exceeds this requirement.