CDL Passing Score: 80% on Each Knowledge Test

What is the passing score for the CDL test?

Eighty percent, on each knowledge test. The federal rule that every state follows says an applicant must correctly answer at least 80% of the questions on each knowledge test to pass it.

What 80% means on each Class A permit test (Washington's counts)
Test	Questions	Correct to pass	Misses allowed
General Knowledge	50	40	10
Air Brakes	25	20	5
Combination Vehicles	20	16	4

Because 80% is a floor set in federal law, no state can set a lower one. States can and do vary the number of questions, so in a state with a 25-question Combination test you need 20 right, and with a 20-question Air Brakes test you need 16. The percentage never changes.

The skills test is scored differently: each of its three parts (vehicle inspection, basic control and road test) is scored by the examiner against the state's checklist, and you must pass each part. The 80% rule applies to the knowledge tests.

Is the CDL test scored as one total?

No. Each knowledge test is its own test with its own pass mark, so a high General Knowledge score cannot make up for a low Air Brakes score.

This is the most common surprise on test day. Someone who gets 47 of 50 on General Knowledge, 19 of 25 on Air Brakes and 17 of 20 on Combination has answered 83 of 95 questions correctly, 87% overall, and still failed Air Brakes by one question.

That is why our practice test reports each part against 80% rather than a single total, and why the study plan starts with the part furthest below the line, not with the subject you like least.

How many questions can I miss on the CDL test?

With Washington's counts, 10 on General Knowledge, 5 on Air Brakes and 4 on Combination Vehicles. The shorter tests leave very little room.

Four misses on a 20-question test is a thin margin. If there are five questions on the trailer air system and you are unsure of two, the rest of the test has to be almost perfect. That is why we suggest aiming for 90% on practice for the two shorter tests, not 80%.

Where do the misses usually come from? On General Knowledge: the numbers (following distance, tread depth, triangle placement), skids and emergencies. On Air Brakes: the leakage limits and pressures. On Combination: which air line does what, and the coupling checks. Each of those is a short list of facts, which is good news.

The numbers most often missed, with sources
Rule	Number	Source
Following distance	1 second per 10 feet of vehicle length below 40 mph; add 1 second above 40 mph	State CDL manual
Tread depth	At least 4/32 inch on front (steering) tires, 2/32 inch on all others	49 CFR 393.75
Low-air warning	Must come on before pressure falls below 60 psi	State CDL manual, air brakes
Spring brakes / tractor protection valve	Come on, or close, between 20 and 45 psi	State CDL manual, air brakes and combinations
Leakage, engine off	Released: under 2 psi a minute (single), 3 (combination). Applied: under 3 (single), 4 (combination)	State CDL manual, air brakes

Clear 80% on every part

Eight full mocks scored part by part against the 80% line, and four drills for each test.

The CDL Pass Pack gives you 8 full mocks on the real clock, 12 drills of 12 questions for the sections that cost you points, and a predictor that turns your mocks into the odds of reaching your target. One payment, no subscription, and your free score stays free.

Prep courses for these tests usually cost $19 to $129. The CDL Pass Pack is US$39 (£29), once.

See the CDL Pass Pack How our questions are built and checked

8
timed mocks: 12
topic drills: 1
score predictor

What happens if I fail a CDL knowledge test?

You retake only the test you failed. Your state sets how soon you can retest, how many attempts you get and whether you pay again, so check its page before you go.

Passed tests usually stay passed while your application is open, so you do not retake them.
Retest waiting periods and fees are state rules; some states let you retest the next day, others make you wait or limit attempts.
If you skip or fail Air Brakes and still get a permit, it carries an air brake restriction until you pass.
If you are in a training program, ask whether a failed knowledge test delays your behind-the-wheel start.

The cheapest retest is the one you do not need. Use the free CDL practice test to check each part clears 80% before you book.

What kind of question costs people the 80%?

Questions with two similar numbers in the options, where the wrong one belongs to a neighboring rule. Two examples follow; the first is worked in full.

CDL-style question 1 · Air brake check
With the engine off and the brakes released, a single truck's air pressure drops 3 psi in one minute. Does it pass the static leakage test?
1. AYes; the limit is 4 psi a minute
2. BNo; the limit is less than 2 psi a minute
3. CYes; the limit is less than 3 psi a minute
4. DNo; there should be no drop at all
Worked answer
B: No; the limit is less than 2 psi a minute. Released (static) leakage must be less than 2 psi a minute for a single vehicle and less than 3 for a combination. 3 psi fails on a single truck.
1. Released or applied? Released (brakes off).
2. Single or combination? Single.
3. Limit: less than 2 psi a minute. 3 psi fails.
The trap: Using the combination or applied limit. Four numbers (2, 3, 3, 4) look alike; tie each to its condition.
CDL-style question 2 · Tires
During your pre-trip inspection, a front (steering) tire has 3/32 inch of tread in its major grooves. What should you do?
1. ADrive; 2/32 inch is the minimum
2. BDrive; any visible tread is legal
3. CDo not drive; front tires need at least 4/32 inch
4. DDo not drive; every tire needs at least 6/32 inch
Show the worked answer
C: Do not drive; front tires need at least 4/32 inch. Federal rules (49 CFR 393.75) require at least 4/32 inch on front tires and 2/32 inch on the others. 3/32 is below the front-tire minimum.
1. Find the tire position: front (steering).
2. Front minimum: 4/32 inch. Others: 2/32 inch.
3. 3/32 is under 4/32, so the tire must be replaced before driving.
The trap: Using the 2/32 rule for every tire. The steering tires get the stricter limit because a front blowout is the hardest to control.

What practice score means I am ready?

Clearing 80% on every part in two different full practice tests, with the shorter tests closer to 90%, is a sensible bar. Our bands are Building (60%+), Close (70%+), At the line (80%+) and Strong (90%+); they are practice labels, not a DMV result.

One good score can be luck, especially on a short test where two easy questions swing it by 10 points. Two scores on different questions are evidence. If you clear 80% on both, the remaining risk is wording, and reading each question twice handles most of that.

For a week-by-week route to that bar, see how to pass the CDL test. For what each test covers, start at the CDL test guide.

Frequently asked questions

Is the CDL passing score the same in every state?

Yes, at least 80% on each knowledge test, because it is set by federal rule. The number of questions can differ.

Is 80% of 50 questions 40?

Yes. You can miss 10 on a 50-question General Knowledge test.

Do I see my score?

It depends on the state: some show the number correct, others only pass or fail. Ask at the office if it matters to you.

Do I have to pass all three tests on the same day?

Usually not. Most states let you take them on different visits while your application is still valid; check your state's rules.

Does the skills test have a passing score?

It is scored by the examiner on each of its three parts; you must pass each part under your state's scoring.

Pass every test the first time

Eight full CDL-style mocks, four drills per test and every answer explained, in one payment.