Ampacity Derating Calculator NEC 310.15
Apply temperature correction and conduit fill adjustment factors to NEC 310.16 base ampacity.
Auto-set by wire type. Override only if your termination rating differs.
By clicking Apply, you acknowledge that results are for reference only and must be verified by a qualified electrician against the current National Electrical Code and local amendments.
Important Notes
Most terminations are rated 75°C. Use the 90°C column as the starting ampacity for derating, but the final derated value must not exceed the 75°C column value unless both terminations are rated 90°C. Equipment grounding conductors and neutrals carrying only unbalanced loads are not counted as current-carrying conductors.
Most terminations are rated 75°C. Use the 90°C column as the starting ampacity for derating, but the final derated value must not exceed the 75°C column value unless both terminations are rated 90°C. Equipment grounding conductors and neutrals carrying only unbalanced loads are not counted as current-carrying conductors.
For reference only. Verify all results with the current NEC and local amendments. See Terms of Use.