EMT, THHN/THWN-2, same-size conductors — the minimum trade size by NEC Chapter 9. Uses the 53% / 31% / 40% fill rule the exam tests. Free, no signup.
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Fill percentages per NEC Chapter 9, Table 1: one conductor 53%, two conductors 31%, three or more 40%. Conductor areas are THHN/THWN-2 from Table 5; EMT internal areas are from Table 4. This tool assumes one conductor size and EMT only — for mixed sizes sum each from Table 5, and other raceways (RMC, PVC) use their own Table 4 areas. Always verify against the current code and your AHJ.
Get the NEC conduit + box fill cheat sheet (Table 1 fill %, Table 4 EMT areas, Table 5 conductor areas) plus 50 free Texas Journeyman practice questions. No spam.
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