CONDUIT
FILL
Fill, voltage drop, and ampacity — straight NEC Chapter 9 and Table 310.16 math, on the edition your jurisdiction actually enforces. 2017, 2020, or 2023: the citations switch with you, down to the renumbered tables.
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The same tables your inspector opens
Fill works exactly the way a plan checker does it: conductor areas from Chapter 9 Table 5 (Table 8 for bare), the fill limit from Table 1, raceway areas from Table 4 for your conduit type — EMT, IMC, RMC, PVC, ENT, or flex. The result is the smallest trade size that passes, with the fill percentage and every conductor's area itemized.
Voltage drop uses the Chapter 9 Table 9 impedance basis for copper and aluminum, single- or three-phase, and tells you both the drop at your length and the maximum run that stays inside the 3% recommendation — which the calculator honestly labels as an Informational Note recommendation, because that's what it is. Ampacity starts from Table 310.16, applies the ambient-temperature correction and the more-than-three current-carrying-conductor adjustment, and caps the answer at your termination temperature per 110.14(C) — the step people forget.
Built from a shipped solver
The fill engine is the same logic that routes real conduit in our paid Revit Conduit Router — ported to the web and parity-checked against NEC Informative Annex C. If you find daylight between this calculator and the code book, use FEEDBACK and we'll chase it down.
Like this math?
Our Revit Conduit Router runs it while it draws the raceway — panel to devices, NEC fill included.
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