NEC Wire Sizing Calculator
ElectricalCalculate proper wire sizes per NEC 2023. Includes ampacity, voltage drop, ambient temperature, conduit fill, terminal rating, and continuous load checks.
How to Use NEC Wire Sizing Calculator
• Select wire type, voltage, and system.
• Input load, run length, temp, and conduit fill.
• Set terminal rating and check if load is continuous.
• Get NEC-compliant wire size with % voltage drop and NEC refs.
Frequently Asked Questions
Is this calculator NEC-compliant?
Yes. It uses NEC 2023 tables for ampacity, derating, voltage drop, and terminal ratings.
What’s the 125% rule?
Per NEC 210.19 and 215.2, continuous loads require wire ampacity ≥ 125% of the load.
What voltage drop limit is used?
3% by default for branch circuits (5% total system), adjustable by user.
Does it support both copper and aluminum?
Yes. Select your conductor material in the input form.
Does it apply ambient and conduit fill derating?
Yes. NEC Table 310.15(B)(1) and (2) adjustments are applied.
Can I override voltage drop thresholds?
Yes. You can customize voltage drop target or disable the check.