← Back to Calculators

Conduit Fill Calculator

Calculate maximum wires per conduit

Maximum Wires Allowed

How It Works

The NEC limits how many wires can fit in a conduit to prevent overheating and allow for easier wire pulling.

The 40% Rule: For 3 or more conductors, the total wire area cannot exceed 40% of the conduit's internal area. For 1-2 wires, it's 53% and 31% respectively.

Why it matters: Overcrowded conduits can cause wire insulation damage, overheating, and code violations.

How to use: Select your conduit type and size, then choose the wire gauge and insulation type you're using. The calculator shows the maximum number of wires allowed per NEC code.