What's the Passing Score on the Iowa CDL General Knowledge Test?
40 out of 50 — 80% — passes Iowa's CDL General Knowledge test. The number itself is federal; what it costs to attempt is Iowa's own story.
One federal number, one all-inclusive fee
49 CFR Part 383 sets the CDL general knowledge test at 50 questions and 80% nationwide, with the Iowa DOT administering that standard rather than writing its own.
Iowa bundles the knowledge test into its $12 CLP fee — there's no separate charge just to sit for the exam, unlike states that bill per test.
Why a lapsed CLP actually costs you
An Iowa CLP is valid for one year with no renewal option. Passing the knowledge test starts that clock, so treat ELDT and the skills test as things to schedule promptly, not indefinitely.
Letting the CLP lapse means reapplying and retaking the knowledge test from zero, even though it only cost $12 the first time.
The material that actually costs points
Air brake PSI thresholds and hours-of-service caps are memorization, not intuition — get the exact number wrong and the question is wrong, no partial credit for being close.
Cargo securement's 50-mile-then-150-mile recheck sequence is a common one to reverse under pressure.
A missed practice question is only useful if you read the full explanation — the correct letter alone teaches nothing.
Frequently Asked Questions
Can Iowa require a higher passing score than 80% for the CDL test?
No. 49 CFR Part 383 fixes the CDL general knowledge test at 50 questions and an 80% passing threshold nationwide — the Iowa DOT administers that federal standard rather than setting its own.
Does the knowledge test cost extra beyond the CLP fee?
No — Iowa's $12 CLP fee already includes the knowledge test.
What score should I aim for on practice tests?
Aim for 90% or higher consistently before your appointment. That buffer above the 80% minimum accounts for first-attempt nerves.
Ready to put this into practice?
Start a free Iowa cdl practice testLast reviewed: 2026-07-22