How to Pass the CDL General Knowledge Test (Miss Budget)

Pass the CDL General Knowledge test by turning the passing score into a number of misses you can afford, then studying only the topics where you lose points. You will leave this page with your own wrong-answer limit, a rule for picking between two true-looking choices, and a simple log that shows what to fix.

The federal rule sets the floor. Under 49 CFR 383.135, you must score at least 80 percent on each knowledge test. Your state decides the question count, the time limit, the fee and the retake wait, so your state's CDL manual is the final word on those.

Turn 80 percent into a wrong-answer budget

A percent is hard to feel while you are testing. A number of misses is simple to track. Do this once:

1. Find the number of questions on your General Knowledge test in your state's CDL manual.
2. Multiply it by 0.80 and round up. That is how many you must get right.
3. Subtract that from the question count. That is the most you can miss.

Write this line and fill it in:

Questions ___ x 0.80 = ___ correct needed. Wrong allowed = ___.

Example: say your test has 40 questions. 40 x 0.80 = 32 correct, so 8 wrong is your limit. Now say your state has 37 questions. 37 x 0.80 = 29.6, which rounds up to 30 correct, so you can miss 7, not 8.

Round down and you plan for one miss too many. That one question can be the whole gap between a pass and a retest fee.

Book when your last two timed tests clear 85 percent

A practice test is exam-style. It is not the exam, and your nerves on test day are different. So aim for room, not for the line.

One good score does not count. Two timed tests in a row tell you more than one lucky one. The 85 is my rule of thumb for a cushion, not a state number.

Many wrong answers are true but incomplete

This is what catches people who read the manual and still miss questions. Two choices can both be true. One covers the whole rule. The other covers a piece of it.

Example, made up to show the pattern: "During a pre-trip inspection, what should you check on a tire?"

• A. Tire pressure
• B. Tread depth
• C. Pressure, tread, and damage such as cuts or bulges
• D. The color of the sidewall

A and B are true facts. But C holds both and adds more, so C is the answer. If you pick A because it sounds right and click, you lose the point.

Four rules for choosing between choices

• Two choices both look true. Ask which one covers the whole rule. Pick the fuller one if every part of it is still true.
• A choice says "all of the above." Test each choice alone. If one is false, "all of the above" is out.
• A choice has "always" or "never." Check it against the manual. One exception makes it wrong.
• You are still stuck. Cross out the choices you can show are false. Pick the fullest one left.

On test day, read every choice to the end before you pick. Reading A, feeling good and clicking is how partial answers get you.

Keep a miss log so you fix the right thing

After each timed practice test, write one line for every miss and give it one of two causes:

• Did not know the rule. You did not have the fact.
• Knew it, picked the partial answer. You had the fact but chose the shorter choice.

Count each group. The bigger group tells you what to do next.

These two causes need different fixes. If your real problem is reading speed and you keep re-studying facts, your score will not move.

You can do this by hand. The Mistake Fixer in the paid program does the re-drilling for you, bringing missed questions back at 1, 3 and 7 days.

Study 30 minutes a day, every day

Kaplan's CDL guide says 30 minutes a day, done every day, beats one long weekend session. That fits a driver with a job or a family. The loop:

1. Get your own state's CDL manual from your state licensing agency. Not a copy from another state.
2. Take a timed practice test to find weak topics.
3. Read only the manual sections for those topics.
4. Retake a timed test and log each miss.
5. Repeat until your last two timed tests are 85 percent or higher.

Study air brakes and combination vehicles with the rest

If you plan to drive a combination vehicle or a vehicle with air brakes, those parts matter. The same federal rule says an applicant who scores below 80 percent on the air brake portion must get an air brake restriction. It also says a score below 80 percent on the combination vehicle portion means no Group A permit or license. How your state applies that is in your manual.

If you miss, the retake rules depend on your state

Maryland is one example. After a first fail, an applicant can retake the next business day if a test appointment is open, and after two or more fails the wait is at least 7 calendar days. Your state may set a different wait or a retest fee, so look it up before you book.

Paying twice is the reason to hold your booking until both timed tests clear 85 percent.

Do this in the next 10 minutes

1. Open your state's CDL manual and find the number of questions on the General Knowledge test.
2. Fill in the line: Questions ___ x 0.80 = ___ correct needed. Wrong allowed = ___.
3. Put that number on a sticky note or in your phone, and check it after every timed practice test.

That is your target. Next you need to know where your misses are.

Find your weak topics before you study

The fastest way to know what to study first is to measure it. The free diagnostic gives you a predicted score and your weak spots in about 10 minutes, with no account. Take the free diagnostic.

FirstTry CDL is not affiliated with any DMV, FMCSA or government agency. Check your state's CDL manual for question counts, fees and retake rules.