NEC Electrical Calculator

The professional-grade NEC electrical calculator built for the job site — not the classroom.

Wire size, voltage drop, conduit fill, box fill, motor circuits, breaker sizing, power factor, and Ohm's Law. All in one electrician calculator. All 100% offline. All referenced to NEC 2023 (NFPA 70).

━━━ WHAT MAKES THIS DIFFERENT ━━━

Every other electrical calculator app gives you a number. This one shows its work.

Run a wire size calculation and you'll see each NEC criterion checked in real time — Table 310.16 ampacity, temperature correction per 310.15(B), CCC derating, termination rule 110.14(C), small conductor rule 240.4(D), and continuous load at 125%. Visible. Auditable.

Most electrician calculator apps skip 110.14(C). That's how you get wire that passes the math and fails the inspection.

━━━ PDF CALCULATION REPORT ━━━

Generate a professional Electrical Calculation Report that cites the NEC code section behind every result. Hand it to your client, your AHJ, or your inspector — a document you can actually leave on the job.

━━━ 8 CALCULATORS INCLUDED ━━━

• Wire Size Calculator — NEC Table 310.16 ampacity, temperature correction 310.15(B), CCC derating, termination rule 110.14(C), small conductor rule 240.4(D), continuous load 125%
• Voltage Drop Calculator — 3% branch and 5% total thresholds, single-phase and three-phase
• Breaker & OCPD Sizing — standard ratings per NEC 240.6(A), EGC sizing per Table 250.122, GFCI alert per 210.8
• Conduit Fill Calculator — NEC Chapter 9 Tables 1, 4 and 5 for EMT, IMC, RMC, PVC Schedule 40, PVC Schedule 80 and FMC
• Box Fill Calculator — NEC 314.16 with full conductor, clamp, device and ground breakdown
• Motor Circuit Calculator — Article 430, full-load current from Tables 430.248/430.250, conductor at 125% FLC, breaker at 250% FLC, overload sizing
• Power Factor — kW, kVAR and kVA triangle with capacitor bank sizing
• Ohm's Law — voltage, current, resistance, power

━━━ WHY ELECTRICIANS SWITCH ━━━

✓ 100% offline — no signal needed in the attic, the basement or the crawlspace
✓ Every result cites the exact NEC section it came from
✓ PDF report you can hand to an AHJ, a client or an engineer of record
✓ The 110.14(C) termination rule applied correctly
✓ NEC 2023 tables
✓ Modern interface — not a UI from 2012

━━━ ONE-TIME PURCHASE. NO SUBSCRIPTION. ━━━

Pay once, use it for the rest of your career. Every future update included.

The free version includes every calculator with no feature limits. The Pro upgrade removes ads and unlocks the PDF Electrical Calculation Report.

━━━ BUILT FOR ━━━

Journeyman and master electricians, apprentices, electrical inspectors, electrical engineers, electrical contractors, and exam prep students who need an NEC-compliant electrical calculator that shows its work.

━━━ LEGAL DISCLAIMER ━━━

NEC® and NFPA 70® are registered trademarks of the National Fire Protection Association (NFPA). This app is an independent product and is not affiliated with, endorsed by, or sponsored by NFPA. All calculations are provided for reference only and are based on NEC 2023. Always verify results against the NEC edition adopted in your jurisdiction and consult a licensed electrical professional before making installation decisions.

Recent changes:
Fixed an issue where the keyboard could cover some input fields, preventing data entry.
Fixed the Terms screen not unlocking on tablets.
General stability improvements.