Electrical Calculators
Free NEC Electrical Calculators
Every calculation cites the specific NEC table and section number. Show-the-math toggles reveal the formula, derating factors, and plain-English explanations.
Wire Size Calculator
Find the correct wire gauge per NEC 310.16 with temperature derating, bundling adjustment, continuous load support, and NEC 110.14(C) terminal temperature enforcement.
Voltage Drop Calculator
Calculate voltage drop percentage for any circuit run length. Includes reverse-solve to find the minimum wire size that meets NEC 3% branch / 5% total recommendations.
Conduit Fill Calculator
Check NEC Chapter 9 conduit fill compliance for any mix of conductors. Supports EMT, IMC, RMC, PVC Schedule 40/80, and ENT with nipple exception.
Box Fill Calculator
Calculate junction box fill per NEC 314.16 including conductors, device yokes, internal clamps, equipment grounding conductors, and terminal blocks.
Conduit Bending Calculator
Calculate bending marks for 7 bend types with interactive SVG diagrams: offset, rolling offset, 3-point saddle, 4-point saddle, 90° stub, back-to-back 90s, and kick with 90.
NewEV Charger Installation Calculator
Size wire, breaker, and panel capacity for Level 2 EV charger installations per NEC 2023 Article 625. Includes GFCI requirements, charging performance, and complete parts list.
NewMCA & MOCP Breaker Calculator
What breaker and wire does this condenser need? Enter the nameplate MCA and MOCP and get the wire size, breaker, ground, and voltage drop per NEC Article 440.
NewElectrical Load Calculator
NEC 220.82 service sizing and the 220.87 existing-load check. Answers the question behind every electrification job: can this panel handle an EV charger or heat pump?
NEC 2026NEC 2026 Changes
What changed from NEC 2023: the Article 120 renumbering, load calc cuts, EV charging, and GFCI expansions. Verified changes and unverified reports, clearly separated.
Updated monthlyNEC Adoption by State
Which electrical code your state enforces right now, all 50 states plus DC, with effective dates and NEC 2026 status. Verified July 2026 and updated monthly.
Reference Charts
Frequently Asked Questions
Which NEC edition do these calculators use?
All calculators reference the NEC 2023 edition (NFPA 70-2023). Specific table and section numbers are cited with every result. Check your local jurisdiction for adopted edition, since some areas still enforce the 2020 or 2017 NEC.
Can I use these calculators for permit applications?
These calculators are educational tools that help you verify your work. Always confirm calculations against the NEC code book and consult with your local AHJ (Authority Having Jurisdiction) for permit requirements.
Why do wire size results enforce the 75°C column?
Per NEC 110.14(C), conductor ampacity is limited by the terminal temperature rating of connected equipment, typically 75°C for most breakers and devices. Even with 90°C-rated wire like THHN, the final ampacity cannot exceed the 75°C column value. The 90°C rating is only used as the starting point for derating calculations.
Running the business side too?
The code math is only half the job. Check your hourly rate against real overhead numbers, or clear up markup vs margin before your next bid.