Mike Holt's Electrical Toolbox vs NEC Load Calculator

Mike Holt, the industry leader in the electrical industry (MikeHolt.com) has created an amazing, practical and useful app for the electrician, inspector, instructor, contractor and engineer. The app contains conductor sizing (including voltage drop limitations), circuit protection sizing, race sizing, equipment grounding conductor sizing for electric heating equipment (commercial and Residential), air-conditioning equipment (commercial and Residential), motors (commercial and Residential), Transformers (commercial) , and dwelling-unit service calculations and sizing.

NEC Load Calculator answers panel sizing, feeder, motor, branch circuit, and cable tray questions directly from the 2023 NEC — with the article citation and math shown for every result. Built for licensed electricians and contractors, not students. CALCULATION MODULES Residential Dwelling unit service sizing per NEC 220.40–220.55 and 220.82. Standard and optional methods. General lighting, small appliance and laundry circuits, fixed appliances, dryer, cooking equipment, HVAC, and service sizing with 230.79(C) minimums. Commercial Feeder and service load calculations per NEC 220.12, 220.44, 220.60, 430.24. Lighting, receptacles, motors, HVAC units, sign circuits, and demand factors. Supports 220/127V and 440/254V systems alongside standard US voltages, with a built-in reminder to verify against NOM-001-SEDE where applicable. Branch Circuit Conductor and OCPD sizing per NEC 210.19, 310.12, 310.15(B)(1)(a). Continuous load handling, conduit fill derating, ambient temperature correction. Covers 120V through 480V circuits, including 127V, 220V, 254V, and 440V. Motor Conductor, overload, and OCPD sizing per NEC 430.22, 430.32, 430.52. Full motor table lookups by horsepower, voltage, and phase. Panel Schedule Circuit-by-circuit panel editor with phase balance, loading percentage, and imbalance calculations per NEC 220.40 and 220.87. Cable Tray Tray fill and ampacity derating per NEC 392.22(A) and 392.80(A). Ventilated trough and solid-bottom tray types, small-cable fill-area limits, and the 90% width rule for large-cable diameter sums. RESULTS SHOW THE CALCULATION Every result includes the NEC article reference, the demand factor table used, and the step-by-step math — not just a final number. Built to be checked against the code book. PANEL LAYOUT Generate a panel layout directly from a load calculation: circuit numbers, breaker sizes, two-pole spans, and spare spaces, arranged the way a real panelboard is wired. Hand off into the full Panel Schedule editor to adjust circuit labels, phase assignment, or breaker sizes. PDF EXPORT Export any result as a PDF report for permit submission, job documentation, or client records.