Conduit Fill Calculator
Calculate how many wires can fit in EMT, PVC, or rigid conduit per NEC tables. Instant fill percentages and capacity checks.
Total Wire Area
0.000 sq in
Conduit Area
0.000 sq in
Fill %
0.0%
Fill Rule
40%
Max Wires @ 40%
0
Status
—
Enter values to calculate
Frequently Asked Questions
What is conduit fill?
Conduit fill refers to the amount of space inside a conduit that is occupied by electrical wires or cables. The NEC (National Electrical Code) specifies maximum fill percentages to prevent overheating and allow for proper wire pulling. Typically, you cannot fill a conduit to more than 40% of its internal area when running three or more wires.
What's the difference between EMT and PVC?
EMT (Electrical Metallic Tubing) is a thin-walled metal conduit that offers protection from physical damage and is typically used indoors. PVC conduit is a non-metallic, corrosion-resistant plastic conduit suitable for both indoor and outdoor use. PVC Schedule 40 is lighter and has a larger internal diameter than Schedule 80, which has thicker walls for higher impact resistance.
What is the 40% fill rule?
The 40% fill rule is an NEC requirement stating that when three or more wires are installed in a single conduit, the total cross-sectional area of all wires must not exceed 40% of the conduit's internal cross-sectional area. For one wire the limit is 53%, and for two wires it is 31%. These limits ensure adequate heat dissipation and room for wire pulling without damaging insulation.