NEC Electrical Calculators
Free online calculators for electricians, engineers, and inspectors. Perform NEC code calculations quickly and accurately.
Conductor & Wire Sizing
Size conductors based on ampacity, voltage drop, and derating factors per NEC Chapter 3.
Raceway & Box Sizing
Calculate conduit fill percentages and box fill volumes per NEC Chapter 9 and Article 314.
Load Calculations
Perform residential and commercial load calculations and breaker sizing per NEC Article 220.
Motor Calculations
Size motor circuits including conductors, overloads, and short-circuit protection per NEC Article 430.
Grounding & Bonding
Size equipment grounding and grounding electrode conductors per NEC Article 250.
Transformer Calculations
Calculate transformer overcurrent protection and conductor sizing per NEC Article 450.
Fault Current
Calculate available fault current at any point in the electrical system per NEC 110.24.
General Purpose
Fundamental electrical calculations including Ohm's Law and power factor conversions.
Specialty Calculators
EV charger sizing, lighting loads, and underground cover depth calculations.
Built for NEC Professionals
Our calculators are designed to help electricians, electrical engineers, contractors, and inspectors perform National Electrical Code calculations quickly and accurately. All calculations reference the applicable NEC articles and tables.
NEC Compliant
Based on NEC tables and formulas with article references shown
Instant Results
Get answers immediately — no sign-up or download required
Mobile Friendly
Use on any device — perfect for field calculations on the job site
Calculators + Practice Questions in One App
Download the NEC Mastery app for all these calculators plus 8,000+ practice questions, quick reference tables, and weighted mock exams.
