FILL ◦ Conduit Fill Calculator

The fastest NEC conduit fill calculator on your phone. Free to try — 3 full calculations on us. One-time $9.99 Pro upgrade. No subscription, ever.

FILL is the conduit fill calculator electricians actually want to use. Built for speed in the field — not a bloated reference app with 50 tabs you'll never open.

FAST, ACCURATE NEC CALCULATIONS Enter your wires, pick your conduit, get your fill percentage instantly. Based on NEC 2023 Chapter 9, Tables 1, 4, and 5. Every number matches the published tables — verify the math yourself.

HOW IT WORKS • Select conduit type and size • Add conductors by type, gauge, and quantity • See fill percentage, wire area, and conduit area in real time • Green/yellow/red status tells you immediately if you pass

FORWARD & REVERSE CALCULATOR Forward mode: "Will these wires fit in this conduit?" Reverse mode: "What's the smallest conduit for these wires?" Both modes show every conduit type ranked by fill percentage with the minimum compliant size highlighted.

SUPPORTED CONDUIT TYPES • EMT (Electrical Metallic Tubing) • RMC (Rigid Metal Conduit) • PVC Schedule 40 • PVC Schedule 80 • IMC (Intermediate Metal Conduit) • FMC (Flexible Metal Conduit) • LFMC (Liquidtight Flexible Metal Conduit)

SUPPORTED WIRE TYPES • THHN/THWN-2 • XHHW • RHH/RHW • THWN All sizes from 14 AWG through 2000 kcmil.

NIPPLE CALCULATIONS Toggle nipple mode for conduit runs 24" or less — automatically applies the 60% fill rule per NEC Chapter 9, Table 1, Note 4.

CALCULATION HISTORY Every calculation auto-saves. Organize by job site area (e.g., "Panel Room", "3rd Floor"). Tap any saved entry to reload it instantly. Label entries for easy reference.

EXPORT & SHARE Copy or share your fill calculation as formatted text — perfect for documentation, inspection prep, or sending to your foreman.

BUILT FOR THE TRADE No ads. No tracking. No subscription. FILL was designed by someone who understands that electricians need tools that work fast and get out of the way. The interface is deliberately simple — big tap targets, high contrast, zero clutter.

FREE TRIAL Try 3 complete calculations for free — no account, no sign-up. See exactly how the app works before spending a cent.

PRO UPGRADE ($9.99 ONE-TIME) • Unlimited calculations • All 7 conduit types • Calculation history with area grouping • Export and share results • One purchase, yours forever. No subscription.

Based on NEC® 2023 Edition. NEC® is a registered trademark of the National Fire Protection Association (NFPA). This app is not affiliated with, endorsed by, or sponsored by NFPA. Calculations are provided for reference and should be verified against the published NEC tables.

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