Conduit Fill Calculator

Calculate conduit fill from total conductor area divided by conduit internal area. Fill % = (Sum of Conductor Areas ÷ Conduit Internal Area) × 100. Compare against NEC Chapter 9, Table 1 limits: 53% for one conductor, 31% for two, and 40% for three or more.

Look up internal area from NEC Chapter 9, Table 4 for EMT, PVC Schedule 40, PVC Schedule 80, RMC, and IMC from 1/2" through 4". For example, 1/2" EMT has 0.304 in² internal area, while 1/2" PVC Sch 40 has 0.285 in² and PVC Sch 80 has 0.242 in².

When fill exceeds the NEC limit, the app recommends the next larger trade size. It also checks the 60% nipple allowance for conduits 24 inches or shorter, and flags when a custom or non-standard size is required.

Jam Ratio = Conduit ID ÷ Conductor OD. A ratio between 2.8 and 3.2 signals a high risk of conductors wedging into a triangular formation and locking during pulling. The app warns on risky combinations and suggests an alternative conduit size or conductor arrangement.

Uses NEC Chapter 9, Table 5 conductor areas for THHN/THWN-2, XHHW, and other common insulation types. Also supports multi-conductor cables treated as a single conductor for fill calculations, and elliptical cables sized by their major diameter.

Generate PDF calculation sheets showing conduit type, trade size, conductor list, total area, fill percentage, pass/fail status, and the applicable NEC Chapter 9 table references. Export to CSV for project documentation. All calculations run offline on-device.