Is 80% on a practice test good enough to book the CDL permit test?

It matches the pass mark, but it leaves no margin. A safer line is 90% or higher, three times in a row, on different days. Practice questions may also be easier or harder than the ones you get.

How many practice tests should I pass before the real test?

There is no official number. A practical rule is three full, timed tests in a row at 90% or higher, with the lowest at 85% or higher. Do it for each test you need.

How many questions can I miss on the General Knowledge test?

If your test has 50 questions and the pass mark is 80%, you can miss 10. Your state sets the question count, so check your state's CDL manual.

Do I need to be ready for the endorsement tests too?

Yes. Each knowledge test is graded on its own, and 80% applies to each one. A weak air brake or combination score has its own cost, even if General Knowledge went well.

What if I fail the permit test?

Retake rules, fees and waiting times depend on your state. Look them up in your state's CDL manual before you book, so you know what a fail would cost.

Can the free diagnostic tell me if I am ready?

It gives you a predicted score and your weak spots in about 10 minutes, so you know what to study first. Use it as a starting point, and then confirm with timed practice tests.

Ready for the CDL Permit Test? A 9-Point Checklist

You are ready to book your CDL permit test when you score about 90% or higher on timed, full-length practice tests three times in a row, on three different days, for every test you plan to take. If you can do that, book it. If you can't yet, this page shows you what to fix first.

The pass mark is 80%. Federal rule 49 CFR 383.135 says you must answer at least 80 percent of the questions correctly on each knowledge test. But 80% in practice leaves you no room for nerves, a tricky question, or a topic you only half know. That is why the safer line is 90%.

Use this checklist: tick every box before you book

Do this on your phone, with a notes app or a piece of paper.

I know which tests I need (General Knowledge plus any endorsements). If you are not sure, start with Which CDL Tests Do I Need?.
I looked up the question count for each test in my state's CDL manual.
I took each practice test timed, with no manual and no notes open.
My last 3 full tests for each test were all 90% or higher.
The lowest of those 3 was 85% or higher.
Those 3 tests were on 3 different days.
I did not retake the same question set until I remembered the answers.
My misses are spread out. No single topic shows up in my misses twice.
I know my state's retest fee and how long I would wait after a fail.

The "lowest score is 85% or higher" line is a rule of thumb I use, not a published standard. It catches the person who got one lucky 95% between two 82% scores.

Work out your pass mark in 30 seconds

Each test is graded on its own. The formula:

Correct answers needed = number of questions x 0.80

A study guide from driving-tests.org lists the General Knowledge test as 50 questions with an 80% pass mark. So you need 40 right and can miss 10. Question counts for the other tests change by state. Check your state's manual, or read How Many Questions Are on the CDL Test?.

Now set your own target. At 90%, you can miss at most 5 questions out of 50. That is your booking line.

Treat 80% to 89% as "not yet", and fix the misses first

Example: say your General Knowledge scores are 84%, 86% and 88% over three days. That sounds close. But 84% is 42 out of 50, only 2 questions above the pass line. One bad day and you are under.

Here is what to do, by score:

Your last 3 full tests	What to do
All 90% or higher, on different days	Book the test
Average 90% or higher, but one test under 85%	Take 2 more tests on new days, then check again
80% to 89%	Do not book. Re-drill your misses, then retest with new questions
Under 80% on any test	Do not book. Go back to the manual for that topic
One test much lower than the rest (for example Air Brakes)	Fix that test first. The others do not make up for it

Study-site advice says the same thing: once you score above 90% consistently, you can take the General Knowledge test whenever you are ready.

Check every test separately: a strong General Knowledge score does not cover Air Brakes

The 80% mark applies to each test on its own. It is not an average. And the cost of a weak section is real:

If you score under 80% on the air brake part, the federal rule says your permit or license gets an air brake restriction.
If you score under 80% on the combination vehicle part, you cannot be issued a Group A permit or license.

Both points come from the same 49 CFR 383.135 rule. So if you need air brakes, do not stop at General Knowledge. Read CDL Air Brakes Test: What It Covers and the Numbers and test that section by itself.

Know what a failed test costs before you book

Rules, fees and waiting times change by state. Driving-tests.org explains that when you can retake the CDL permit test after a fail depends on the state. As one example only, Kentucky's statute lists a $50 retesting fee. Other states differ.

Use this to add up your own cost:

Cost of one fail = retest fee + days you wait + work you miss

Example: say your state charges $50 and you lose one day of work worth $160. One failed attempt costs you about $210, plus the wait. Three more days of study cost you evenings. If you are at 84%, the evenings are the better deal.

Four mistakes that make people book too early

Booking after one good score. One 94% can come from questions you saw before. Wait for three.
Retaking the same set. Your score goes up because you remember the answers, not because you know the rule.
Studying with the manual open. The real test will not let you look anything up.
Averaging tests together. A 95% on General Knowledge does not fix a 70% on Air Brakes.

Ask what you keep missing, not just what you scored

After each test, write down every miss and the topic it came from. Two misses in the same topic mean you do not know that topic yet. Go back to the manual for that section, read it once, and then answer new questions on it the next day.

Answers that look right but are incomplete trip up a lot of people, especially if English is your second language. When you miss one, read the whole question again and ask: what part did I skip? Is the CDL Written Test Hard? covers that problem too.

Copy this miss log into your notes

After every timed test, add one line for each question you missed. Use this format:

Date | Test | Topic | Why I missed it | Fix

Example: say you write "Oct 7 | Air Brakes | Stopping distance | Mixed up the numbers | Re-read the section, redo 10 questions tomorrow". After a week, sort the lines by topic. The topic that shows up most is what you study next. The topic that disappears from the log is done.

Do this in the next 10 minutes

Open your state's CDL manual and find the question count for each test you need.
Write down: correct answers needed = questions x 0.80.
Find your state's retest fee and wait time.
Take one timed practice test with nothing open.

That fourth step tells you where you are today. If you would rather not guess, the free diagnostic does a version of this for you.

Not sure where you stand? Take the free diagnostic

FirstTry CDL's free diagnostic takes about 10 minutes, needs no account, and shows you a predicted score and your weak spots, so you know what to study first. You can also try one 10-question practice test for each test type and read all the guides for free. The questions are exam-style and built from the official CDL manual, and FirstTry CDL is not affiliated with any DMV or government agency.

Take the free diagnostic