--- title: "How Hard Is the C-10 Exam? What CSLB's Own Documents Show" description: "Two closed-book exams, 3½ hours each, four choices per question, no published pass rate. What makes the C-10 hard, what makes it easier, and CSLB's own sample math question, worked out." url: https://caelectricalprep.com/blog/how-hard-is-the-c10-exam published: 2026-10-15 topic: "Exam" language: en license: "Free to read and quote with attribution to CA Electrical Prep (https://caelectricalprep.com)." source_of_truth: "2025 California Electrical Code (Title 24, Part 3), which adopts the 2023 NEC with California amendments." --- # How Hard Is the C-10 Exam? What CSLB's Own Documents Show Two closed-book exams, 3½ hours each, four choices per question, no published pass rate. What makes the C-10 hard, what makes it easier, and CSLB's own sample math question, worked out. ## Key points - You must pass two closed-book exams, the C-10 trade exam and Law and Business, with 3½ hours for each. - CSLB publishes no pass rate and no passing percentage. Anyone who quotes one is guessing. - Planning and Estimating (28%) and Rough Wiring (27%) are more than half the trade exam, and some questions need math. - Law and Business is a whole second exam, and none of it is wiring. - There is no penalty for guessing, a calculator will be provided, and a failing report shows your score by section. The C-10 is hard in a specific way, not a mysterious one. You have to pass two closed-book exams, the C-10 trade exam and the Law and Business exam, with 3½ hours for each and four choices per question, and CSLB does not publish a pass rate or a passing percentage for either. What makes people fail is predictable: walking in cold on Law and Business, weak math on the planning and estimating questions, and reading the trade from field habit instead of from the code. Each of those is fixable before exam day. ## Key facts | Fact | Value | Source | |---|---|---| | Exams to pass | Two: Law and Business, and the C-10 trade exam | CSLB, Get Licensed to Build | | Time | 3½ hours for each | CSLB Examinations FAQ | | Books allowed | None. Closed book | CSLB C-10 study guide | | Question style | Four choices, only one BEST answer; some questions need math | CSLB C-10 study guide | | Passing percentage | Not published; it "varies for each exam" | CSLB, Get Licensed to Build | | Biggest trade sections | Planning and Estimating (28%), Rough Wiring (27%) | CSLB C-10 study guide | | Retake wait | 21 calendar days | CSLB Examinations FAQ | ## What makes it hard ### It is closed book The C-10 study guide lists the 2025 California Electrical Code, the American Electricians' Handbook and the Cal/OSHA safety orders among its references, and then says it is a closed-book examination: no reference materials may be used. Whatever you need from those books has to be in your head. ### It asks for the BEST answer Questions are written to provide only one BEST answer, with four choices each. On a hard question, two answers will look right. Field experience gets you to "this would work"; the exam wants "this is what the code requires." ### More than half of it is planning, estimating and rough wiring Planning and Estimating (28%) and Rough Wiring (27%) are the two biggest sections. Planning and Estimating covers electrical calculations, code requirements and material selection, and some questions require mathematical computation. CSLB's own sample question: a contractor needs 13 receptacles that cost $3.56 each plus sales tax of 7.25%, and the supplier gives one free for every 10 purchased. The answer is $45.82: you pay for 12 receptacles, $42.72, plus the 7.25% sales tax. That is the kind of arithmetic that costs points when you rush it. ### Law and Business is a whole second exam All applicants must pass the law and business exam as well as the trade exam. It has seven sections, led by Contract Requirements and Execution (21%) and Employment Requirements (20%), and none of it is wiring. An electrician who studies only the trade is walking into half the requirement unprepared. See [what is on the Law and Business exam](/blog/law-and-business-exam-guide). ### Nobody tells you the cutoff CSLB's guide answers "What percentage is needed to pass the exam?" by saying applicants can ask CSLB, as it "varies for each exam." If you pass, you are told you passed but are not given detailed information about your score. So you cannot aim to scrape by. You have to be solid across every section. ## What makes it easier - **The weights are published.** CSLB tells you exactly how much of the exam each section is worth. Study in that proportion. - **There is no penalty for guessing.** Never leave a question blank. - **A calculator will be provided.** You need to know the setup, not do long division by hand. - **Failing tells you where to look.** If you fail, you see how well you did on each section, and you can retake after 21 calendar days. - **Law and Business comes in Spanish.** CSLB offers a Spanish version of Law and Business. The C-10 has none, but CSLB can approve a translator to read it to you. ## So how hard is it, really? CSLB does not publish pass rates, so anyone who quotes you one is guessing. What the official documents do show is that the exam rewards a particular kind of preparation: the code as written, the math done carefully, and Law and Business studied as seriously as the trade. An electrician with the four years of journey-level experience CSLB requires already has the field knowledge. The work is turning it into code-exact answers under a clock. For every official rule in one place, see [C-10 exam facts, with the CSLB source](/blog/c10-exam-facts). ## Sources - [CSLB License Examination Study Guide: Electrical (C-10)](https://www.cslb.ca.gov/resources/studyguides/c10studyguide.pdf) - [CSLB License Examination Study Guide: Law and Business](https://www.cslb.ca.gov/Resources/StudyGuides/LawStudyGuide.pdf) - [CSLB Examinations Frequently Asked Questions](https://www.cslb.ca.gov/About_us/Examination_FAQ.aspx) - [CSLB, Get Licensed to Build](https://www.cslb.ca.gov/Resources/GuidesAndPublications/GetLicensedToBuild_ENG0525_ADA.pdf) _Last reviewed: 2026-10-15. Every fact above is quoted from the CSLB document it cites and checked by code against our stored copy of that document._ ## Find out how hard it is for you Take the [free 10-question C-10 practice test](/free-exam). It shows you, section by section, where you would lose points today, across both the trade and Law and Business topics. No account needed. The full course is $148.75 one time: lessons for both exams, practice questions with written explanations, and timed practice exams, in English and Spanish. [See what is included](/pricing). ## Questions and answers ### Is the C-10 exam hard? It is demanding because it is two closed-book exams with four choices per question and one BEST answer, and the trade exam leans on code-exact knowledge and math. It is predictable, though: CSLB publishes every section and its weight. ### What is the pass rate for the C-10 exam? CSLB does not publish one in its study guides, its exam FAQ, or its Get Licensed to Build guide. Treat any number you see as someone else's estimate. ### What is the hardest part of the C-10 exam? For many electricians it is the Law and Business exam, because none of it is wiring. On the trade exam, Planning and Estimating (28%) and Rough Wiring (27%) are the two biggest sections. ### Is there math on the C-10 exam? Yes. CSLB says some questions require mathematical computation, and a calculator will be provided. --- Canonical HTML version: https://caelectricalprep.com/blog/how-hard-is-the-c10-exam More: https://caelectricalprep.com/llms.txt