Tools · Wire Ampacity
Wire Ampacity Calculator
Look up allowable ampacity from NEC Table 310.16 for copper or aluminum, then apply ambient-temperature correction and conductor-bundling adjustment.
How it’s calculated. Base ampacity is NEC Table 310.16 (not more than three
current-carrying conductors, 30°C/86°F ambient). The ambient correction uses
√((Tc − Ta) ÷ (Tc − 30)) (matching Table 310.15(B)(1)); bundling uses Table 310.15(C)(1)
(4–6 = 80%, 7–9 = 70%, 10–20 = 50%, …).
Terminations are commonly listed for 75°C — don’t exceed the 75°C column at the lugs. Small conductors are also limited by 240.4(D) (14 AWG Cu = 15 A, 12 AWG Cu = 20 A, 10 AWG Cu = 30 A). This is a sizing aid, not a substitute for an engineered design.
Need it engineered and stamped?
Sizing conductors for a commercial build? Talk to a commercial electrician in Tucson — we design it, stamp it, and install it across Arizona.
Request a Bid