Conduit Fill Calculator

NEC conduit fill rules

The National Electrical Code limits how much of a conduit's internal area can be occupied by conductors. These limits prevent overheating and make it possible to pull wires without damaging insulation.

Fill percentage limits

For 1 conductor: maximum 53% fill. For 2 conductors: maximum 31% fill. For 3 or more conductors: maximum 40% fill. These thresholds come from NEC Chapter 9, Table 1.

Supported conduit types

This calculator covers all major conduit types: EMT (Electrical Metallic Tubing), IMC (Intermediate Metal Conduit), RMC (Rigid Metal Conduit), PVC Schedule 40, and PVC Schedule 80. Internal areas are sourced from NEC Chapter 9, Table 4.