NEC Electrical Code Calculations, Schedules, and Worksheets

Sizing a service, picking a conductor, or sizing a grounding electrode conductor should not require re-deriving the National Electrical Code from first principles every time. This guide walks through the calculations electricians, electrical engineers, inspectors, and students actually run in the field — worked from the use-case question all the way to a Code-compliant answer, with every step tied to the specific NEC article or table that supports it.

Chapter 1 covers residential load calculations: a full single-family dwelling service calculation under the Standard Method, and a 12-unit multifamily building under the Article 220.84 optional method — including where demand factors apply, where they don't, and how they compound.

Chapter 2 covers conductor sizing end to end: base and adjusted ampacity, voltage drop, overcurrent protection and the 125% continuous-load rule, motor branch-circuit conductors, feeder and service entrance conductors, and grounding electrode, equipment grounding, and neutral conductor sizing.

Every project includes a project brief, a step-by-step worked calculation, a summary table, and field notes flagging the judgment calls and code-edition dependencies a working engineer needs to watch for. This is a study and field-reference aid, not a replacement for the Code — always verify citations against the NEC edition adopted in your jurisdiction.