NEC Code Exam Study Guide: Key Articles & Calculations
The journeyman electrician exam is an open-book test — but only if you know where to look. The National Electrical Code is nearly 1,000 pages, and the exam rewards candidates who understand the structure of the code and can apply its math quickly. This guide covers the articles that appear most on licensing exams, the calculations you must know cold, and the fastest way to prepare.
Take the free NEC code aptitude practice testWhat is the NEC and why does it matter?
The National Electrical Code (NFPA 70) is the minimum standard for safe electrical installations in the United States. It is updated every three years and adopted — with occasional amendments — by states, counties, and municipalities as law. When you work as a licensed electrician, you are legally responsible for knowing the current adopted version in your jurisdiction. The journeyman exam tests that knowledge directly: you will be given a copy of the NEC and asked to answer questions by finding and applying the correct articles. Speed matters — knowing where articles live is as important as understanding what they say.
Most tested NEC articles on journeyman exams
Article 90 defines the purpose and scope of the NEC — read it first, because it explains what the code does and does not cover. Article 100 (Definitions) and Article 110 (Requirements for Electrical Installations, including 110.3(B) on listed equipment) appear throughout exam questions. Article 210 (Branch Circuits) covers the continuous-load rule, AFCI requirements (210.12), and GFCI locations (210.8). Article 230 covers service entrance. Article 240 covers overcurrent protection and the sizing rules for breakers and fuses. Article 250 (Grounding and Bonding) is heavily tested — especially the distinction between grounding (connecting to earth) and bonding (connecting metal parts to ensure fault current returns to the source). Article 300 covers general wiring methods. Article 310 covers conductor ampacity, temperature corrections, and bundling derating — Table 310.15(B)(16) and Table 310.15(C)(1) are tables you will use on almost every exam. Article 314 covers outlet, device, and junction boxes, including box fill calculations from Table 314.16(B). Article 430 covers motors and their overcurrent protection rules.
NEC calculations you must know
Load calculation: Use I = P ÷ V to find current, P = V × I to find power, and V = I × R (Ohm's Law) to find voltage. Continuous-load rule: a continuous load (on for 3+ hours) must not exceed 80% of the overcurrent device's rating — equivalently, the device must be rated at 125% of the load (NEC 210.20, 215.3). Ampacity derating: when 4–6 current-carrying conductors share a raceway or cable, multiply the Table 310.15(B)(16) ampacity by 0.80; for 7–9 conductors, multiply by 0.70 (NEC Table 310.15(C)(1)). Box fill: sum the cubic-inch volumes from Table 314.16(B) — each unbroken conductor counts as one volume for its size; all equipment grounding conductors together count as one conductor at the largest EGC size in the box; yoke-mounted devices count as two conductors at the largest conductor attached. Voltage drop: VD% = (VD ÷ Source Voltage) × 100. NEC informational notes recommend limiting branch-circuit voltage drop to 3% and the combined feeder-plus-branch drop to 5%.
How journeyman exams are structured
Most state journeyman exams are administered by PSI Exams or Prometric and consist of 80–100 multiple-choice questions with a 4-hour time limit. They are open-book — you bring your own NEC (and sometimes other code books), tabbed and highlighted. No hand-written notes are allowed in the margins. Questions fall into two broad types: code comprehension (find the article, read the rule, pick the answer) and applied math (use a formula, look up a table value, calculate the answer). A passing score is typically 70–75% depending on the state. Some states require a separate exam for commercial/industrial work or for specific license levels (residential, limited energy, master).
Study strategy
Step one: obtain the exact code edition your state tests and tab every chapter. Practice finding articles quickly — the exam rewards speed as much as knowledge. Step two: memorize the most-used tables (310.15(B)(16) ampacity, 314.16(B) box fill volumes, 310.15(C)(1) derating factors) so you can look them up in seconds. Step three: drill calculations until the formulas are automatic — load calcs, derating, and box fill appear on almost every exam. Step four: take timed practice tests under open-book conditions. If you spend more than 2 minutes on a question, mark it and move on — you can return to hard questions after securing the easy points. Step five: for code-comprehension questions, read the NEC article as your sole authority — ignore field habits and answer only what the article actually says.
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Start the practice test →Frequently Asked Questions
Is the journeyman exam open book?
Yes — most state journeyman electrician exams allow you to bring a copy of the NEC (and sometimes other approved code books). However, hand-written notes in the margins are typically not allowed, and the exam is timed, so you must be able to find articles quickly. Pre-tabbing and highlighting your code book before test day is essential.
Which NEC edition should I study?
Study the edition currently adopted by your state. As of 2026 most states have adopted the 2020 or 2023 NEC, but adoption varies — check your state electrical licensing board's website for the specific edition tested. The exam booklet and testing provider will specify which edition is permitted.
How many times can I retake the journeyman exam?
Retake policies vary by state. Most allow multiple attempts but require a waiting period between tests — commonly 30 to 90 days. Some states charge a full retest fee each time. Check your state licensing board for your specific rules, and use each attempt as diagnostic data to focus your next round of study.
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