NEC (NFPA 70) — National Electrical Code Standards Hub
The National Electrical Code (NFPA 70) is the dominant U.S. electrical-installation standard, adopted into law by every state and most municipalities. This page is the cross-reference: every calculator and reference page indexed by the NEC article and clause it implements. Reviewed by a licensed PE.
NEC article cross-reference
Every page that implements an NEC requirement, organised by article. Use this as the index when verifying that a calculator output matches the code clause your AHJ requires.
| NEC clause | Topic | Pages |
|---|---|---|
| Article 100 | Definitions | Voltage, Ampere, Watt |
| Article 110 | General requirements (incl. AIC ratings) | Circuit breaker sizes, AC cables |
| Article 210 | Branch circuits — 1.25× continuous-load factor | Wire sizing for amps, Sizing of wire, Amp-hour calculator |
| Article 215 | Feeders | Wire size calculator, Voltage drop calculator |
| Article 220 | Branch-circuit and feeder calculations | How to calculate power, Calculate (aggregate) |
| Article 230 | Service entrance | Service-entrance reference (in /wire/) |
| 240.4 / 240.4(D) | Conductor protection — small-conductor rule | Wire sizing for amps, Square D 20A breaker |
| 240.6 | Standard ampere ratings (15, 20, 30… A) | Circuit breaker sizes |
| 250.20 / 250.26 | Grounding for wye and corner-grounded delta | Three-phase reference |
| 250.122 + Table | Equipment grounding conductor sizing | Sizing of wire |
| 300.5 | Underground installations — minimum cover | Electrical conduit sizes, AC cables |
| 310 (310.15 / 310.16 / 310.17) | Conductor ampacity tables | Wire size calculator, AWG size chart, Amp-wire chart, 4 AWG copper |
| 342 / 344 / 348 / 352 / 358 | Conduit articles — IMC / RMC / FMC / PVC / EMT | Electrical conduit sizes |
| 358.26 / 344.26 | Conduit bend limits — 360° between pull points | Electrical conduit sizes |
| 392 | Cable trays | AC cables |
| 402 / 400 | Fixture wires & flexible cord (small AWG) | Sizing of wire |
| 408 | Switchboards and panelboards | Three-phase reference |
| 430 (.6, .22, .52, .250) | Motor branch circuits + FLA tables | Electric motor FLA, FLA on a motor, 3-phase motor branch |
| 440 (.4, .22) | HVAC AC units — MCA / MOP rules | MCA / MOP for HVAC |
| 460 | Capacitors — overcurrent + discharge resistor | Capacitor reference, Power factor calculator |
| 680 | Swimming pools — bonding and equipotential grid | Sizing of wire (pool pump) |
| 690 | Solar PV systems — DC wire sizing | AC cables, Battery sizes |
| Chapter 9 Tables | Conduit fill (Tables 1, 4, 5, 8, 9) | Electrical conduit sizes, AWG ↔ mm² conversion |
About the NEC
NFPA 70 is published by the National Fire Protection Association in Quincy, Massachusetts. The first edition appeared in 1897 to consolidate dozens of conflicting municipal electrical codes adopted in the wake of the Edison-Westinghouse "war of currents". Today NFPA 70 is updated on a three-year cycle by NEC technical committees representing electricians, manufacturers, AHJs, insurers, fire investigators, and academic engineers.
The NEC is not a federal law — it is a model code that becomes legally enforceable when adopted by a state or local jurisdiction. As of 2024, all 50 U.S. states have adopted some edition (most are on 2017, 2020, or 2023). Always confirm with your local AHJ which edition applies and whether any local amendments override default code.
NEC editions and adoption status
| Edition | Published | Adoption status (2024) |
|---|---|---|
| NEC 2014 | 2013 | Some legacy jurisdictions |
| NEC 2017 | 2016 | ~10 states |
| NEC 2020 | 2019 | ~30 states (most common) |
| NEC 2023 | 2022 | ~10 states adopted; growing |
| NEC 2026 | Expected late 2025 | Comments pending |
Related standards
How to obtain the NEC
The official NFPA 70 PDF is sold by the National Fire Protection Association — single licence approximately $90 USD. Free read-only access is available through the NFPA Link platform (sign-up required). Many libraries carry print copies in their reference collection. Code-officials and licensed electricians often have shared organisational access through their employer.
The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. This Code is not intended as a design specification or an instruction manual for untrained persons.