Derating Calculator — Free Online Calculator
Calculate ampacity derating for bundled conductors per NEC 310.15(C). Enter conductor count for the derating factor.
How to Use This Calculator
Enter the base ampacity of the conductor and select the number of current-carrying conductors bundled together.
The Formula Explained
NEC 310.15(C)(1) requires reducing conductor ampacity when more than 3 current-carrying conductors are bundled in a raceway or cable. More conductors generate more heat, requiring each to carry less current.