How Many Questions Are on the Illinois CDL General Knowledge Test?
The Illinois CDL general knowledge test has 50 multiple-choice questions, and you need to answer at least 40 of them correctly (80%) to pass. This format is set by federal rule and is the same across nearly every state, including Illinois.
The official test format
Unlike a state's regular driver's license knowledge test, the CDL general knowledge test's length and passing score are set by federal regulation (49 CFR Part 383), which is why Illinois' format matches most other states exactly.
The test covers core commercial driving topics common to nearly every CDL applicant nationwide, including vehicle inspection, basic vehicle control, air brakes, cargo securement, and hours-of-service rules.
Because Secretary of State procedures can still vary in scheduling and required documentation, always confirm the current process on the official Illinois SOS website before your appointment.
How the questions are distributed by topic
The official test draws from a broad range of federally-defined topics rather than any single area, which is why understanding the reasoning behind each rule matters more than memorizing isolated facts.
Our free Illinois CDL practice tests cover 17 topic areas, including hours-of-service, HazMat awareness, combination vehicles, and accident procedures, so you can see which areas need more review before test day.
How our practice tests are structured
Rather than mirroring the exact 50-question format, dmvwrittenexam.com splits its 100+ original Illinois CDL questions into multiple practice tests, so you get more total repetitions across more topics than a single official-length test would allow.
Each question includes an explanation and a source reference, so you learn the reasoning behind the correct answer rather than just memorizing it.
Frequently Asked Questions
Is the Illinois CDL test the same length as in other states?
Yes, generally. The CDL general knowledge test's 50-question, 80%-passing format is set by federal rule and is consistent across nearly every state.
Are there other knowledge tests besides the general knowledge test?
Yes, endorsement-specific tests (such as for air brakes, combination vehicles, or hazardous materials) may also be required depending on the type of CDL and endorsements you're pursuing. Confirm current requirements with the Illinois SOS.
What happens if I don't pass the CDL general knowledge test?
Retake policies, including any waiting period or fee, are set by the Secretary of State's office and can vary. Check with your local SOS facility for current retake rules.
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Start a free Illinois cdl practice testLast reviewed: 2026-07-14