Conduit Fill Calculator (NEC)

This calculator finds how many same-size cables fit inside a conduit within standard fill limits. It applies the accepted fill ratios (53 percent for one cable, 31 percent for two, 40 percent for three or more) to the conduit and cable cross-sections. Enter the conduit inner diameter, the cable outer diameter, and the count to get the maximum the conduit holds and the conduit size your pull needs.