Ampacity Calculator

NEC Table 310.16 base ampacity, then derated for ambient temperature and conductor bundling — the way the exam asks it. Free, no signup.

Base ampacity per NEC Table 310.16 (conductors in raceway/cable, 30°C ambient). Ambient correction per Table 310.15(B)(1); bundling adjustment per Table 310.15(C)(1), applied when more than 3 current-carrying conductors. Final conductor selection is still limited by the termination temperature rating (110.14(C)) and the overcurrent rules of 240.4 — this tool estimates ampacity, it does not size the breaker.

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Journeyman Wireman · Texas Journeyman exam prep · for study estimates, not a substitute for engineered design