TrueFill: Conduit Fill

TrueFill is a conduit-fill calculator built for electricians who want a clean answer and the math behind it - not just a number.

Pick a raceway type, add your phase, neutral, ground, and spare conductors, and TrueFill returns the smallest passing trade size, the fill percentage against the allowable fill rule, the remaining area, and a full math trace you can check line by line.

WHAT YOU GET
- Smallest passing conduit and fill headroom in seconds
- Conduit candidates compared, with pass/fail and room to spare
- Show Math: conductor-area breakdown, assumptions, and source references
- Save drafts and reopen the exact revision later
- Quick-setup templates for 3-phase feeders, 1-phase branches, and control/spare runs

BUILT FOR THE FIELD
Dark, mobile-first, and fast to enter. Every result shows its inputs and assumptions so you can verify before you pull wire.

This version ships with demo code data only. Results are clearly labeled as a demo/estimating aid and are intentionally blocked from final, export-ready, BOM, pricing, and bid-total use. Always verify against the NEC and your project documents.

TrueFill is a calculation aid for qualified electrical professionals and is not a substitute for the NEC, a licensed engineer, or a code-compliance determination.

From 509 Electric.