How Many #12 THHN Fit in 3/4" PVC-40?

Maximum #12 THHN conductor count for 3/4" PVC-40 at the NEC 2023 40% fill cap (3 or more conductors).

In a 3/4" PVC-40, the NEC 2023 ceiling is 15 #12 THHN conductors. The code permits 40% of the conduit's 0.5080 in² interior to be filled when three or more conductors share the raceway (NEC Chapter 9, Table 1), which leaves 0.2032 in² of usable area; each #12 THHN takes 0.0133 in², so 0.2032 ÷ 0.0133 rounds down to 15. This is a fill limit, not an ampacity rating: every current-carrying conductor counts toward the total — including a neutral that carries current — and once more than three current-carrying conductors share the conduit you must also apply the ampacity adjustment factors in NEC 310.15(C)(1). THHN, THWN-2 and XHHW-2 share the same Table 5 cross-section, so the count is identical; RHH and RHW-2 are larger and fit fewer. On long or multi-bend pulls, plan pulling tension and lubricant even when the fill math says the conductors fit.