Conduit Fill Calculator (NEC-Style % Fill)

How to use

1. Choose conduit type: EMT, RMC/IMC, PVC Schedule 40 or 80.
2. Pick the trade size and the wire size you are pulling.
3. Enter how many wires go in the run; tick the nipple box only for runs 24 in or shorter.
4. Read the fill percentage and pass/fail — and the next size up if it fails.

About this tool

Pulling too many wires through one raceway is a code violation and a cable-damage risk, and eyeballing it never works. This conduit fill calculator applies the NEC Chapter 9 logic: 53 percent fill for a single conductor, 31 percent for two, and 40 percent for three or more, using approximate internal areas for EMT, rigid metal conduit and PVC in Schedule 40 and 80, from half-inch through four-inch trade sizes. Pick your conduit type and size, your wire from 14 AWG up to 500 kcmil, and the conductor count; you get the fill percentage, a clear pass or fail against the applicable limit, and — if it fails — the next trade size up that works, including the 60 percent nipple allowance for runs 24 inches or shorter. Areas here are approximations, so always verify against the current NEC tables before inspection. Everything computes locally in your browser; nothing you enter leaves the page.

FAQ

Rate this tool

Your rating stays in this browser (local storage) — nothing is sent to any server.