FILL ◦ Conduit Fill Calculator

Now supports NEC 2026 and 2023. The fastest conduit fill calculator built for the field, not a reference app. Try 5 full calcs free, then a one-time Pro unlock.

The conduit fill calculator electricians actually reach for on the job.

Now built for both NEC 2026 and NEC 2023. Same verified fill tables, switch editions in a tap, work to whichever code your inspector goes by.

Enter your wires, pick your conduit, get your fill percentage. That's the whole app.

FAST, ACCURATE NEC CALCULATIONS Based on NEC Chapter 9, Tables 1, 4, and 5. Every number matches the published tables, and you can check the math yourself. NEC 2026 and 2023 use the same fill values, so the answer is right either way.

FORWARD & REVERSE Forward: "Will these wires fit in this conduit?" Reverse: "What's the smallest conduit for these wires?" Reverse mode ranks every conduit type by fill percentage and highlights the smallest compliant size.

HOW IT WORKS

• Select conduit type and size
• Add conductors by type, gauge, and quantity
• See fill percentage, wire area, and conduit area update as you go
• Green, yellow, or red tells you at a glance whether you pass

CONDUIT TYPES EMT, RMC, IMC, FMC, LFMC, PVC Schedule 40, and PVC Schedule 80.

WIRE TYPES THHN/THWN-2, XHHW, RHH/RHW, and THWN from 14 AWG through 2000 kcmil, plus TFN/TFFN fixture wire in 16 and 18 AWG for controls and low-voltage lighting work.

NIPPLE CALCULATIONS Flip on nipple mode for runs 24 inches or shorter and FILL applies the 60% fill allowance from NEC Chapter 9, Table 1, Note 4.

CALCULATION HISTORY Every calculation saves on its own. Group them by area of the job, like "Panel Room" or "3rd Floor," label them, and tap any saved entry to load it back instantly.

EXPORT & SHARE Copy or share any calculation as clean, formatted text. Good for documentation, inspection prep, or sending to your foreman.

BUILT FOR THE TRADE No ads. No tracking. No subscription. FILL was made by someone who gets that an electrician needs a tool that works fast and then gets out of the way. Big tap targets, high contrast, nothing you have to dig through.

TRY IT FIRST Run 5 complete calculations free. No account, no sign-up. See how it works before you spend anything.

PRO UPGRADE ($7.99, ONE TIME)

• Unlimited calculations
• All 7 conduit types
• Calculation history with area grouping
• Export and share
• Buy once, keep it for good. No subscription.

Based on the NEC 2023 and NEC 2026 editions. 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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