Solve for Ampacity · Conductor Size · Max Ambient Temp · Max Conductor Count · NEC 2026 Art. 310
Reverse of NEC Table 310.15(B)(16)-310.20
Disclaimer — Important
These reverse scenarios invert NEC Tables 310.15(B)(16)-310.20 (ampacity), 310.15(B)(1)(1)/(B)(2) (ambient temperature correction), and 310.15(C)(1) (conductor count adjustment). The Conductor Size scenario also runs the NEC 110.14(C) terminal-rating check, same two-pass method as the main Wire Size Calculator, taking whichever pass requires the larger conductor. The Ampacity, Max Ambient Temperature, and Max Conductor Count scenarios remain Pass 2 (insulation-rating) only, since they take an already-chosen conductor size as input rather than solving for one.
This calculator is an independent tool intended to assist electrical professionals for educational and estimation purposes only. Results must be verified by a licensed electrical engineer or electrician and reviewed against the full NEC text, equipment listings, and applicable local codes. NEC® and NFPA 70® are registered trademarks and copyrighted publications of the National Fire Protection Association.