CDL General Knowledge Study Guide 2026: Pass the Written Test

Every commercial driving career starts with one written test. Before you touch a truck for your skills exam, before you pick up any endorsement, you have to pass the CDL General Knowledge (GK) test. It's the foundation the entire license is built on — and the good news is it's a straightforward multiple-choice exam you can prep for in a week or two.

This guide covers what the GK test actually is, how it's structured, the topic areas that carry the most weight, the highest-yield rules to memorize, and a study plan that gets you to the 80% you need to pass.

What the General Knowledge test is

The CDL General Knowledge test is the foundational written exam that every commercial driver's license applicant must pass — Class A, Class B, and Class C alike. It's built from the AAMVA Model Commercial Driver License Manual and administered by each state's DMV.

Two things make it the most important test in the process:

• It's the base test for all classes. No matter what you plan to drive — an 18-wheeler, a box truck, a bus, or a delivery vehicle — you take the same General Knowledge exam.
• Passing it gets you the permit, not the license. A pass unlocks your Commercial Learner's Permit (CLP), which lets you practice behind the wheel with a qualified CDL holder before your skills test.

Because it's state-administered from the same national model manual, the content is consistent everywhere, but the exact wording, question count, and time limit vary by state. Always confirm the specifics with your own DMV.

Exam structure

• ~50 multiple-choice questions
• Passing score: 80% — typically 40 of 50 correct
• The 80% threshold is a federal minimum that states cannot lower
• Time limits vary by state
• Questions are drawn randomly from the manual, so no two tests are identical

What it costs

There's no standalone fee for the General Knowledge test itself. It's bundled into your CLP and CDL application fees, which vary by state:

• CLP: roughly $10-100
• Total CDL licensing: roughly $20-150

Prerequisites

• A valid regular driver's license
• 18+ to drive intrastate (within your state); 21+ for interstate driving or to carry hazmat/passengers across state lines
• A DOT medical certification
• Since 2022, Entry-Level Driver Training (ELDT) — both theory and behind-the-wheel — may be required before you can take the skills test. It doesn't block the GK test, but plan for it in your timeline.

The topic areas

The GK test draws from two sections of the model manual — Section 2 "Driving Safely" and Section 3 "Transporting Cargo." The breakdown below is an approximate emphasis, not an official weighting, but it tells you where to spend your time:

The lesson is simple: space and hazard management plus vehicle inspection together make up close to half the exam. If your study time is limited, that's where it goes.

The highest-yield material

These are the concepts that show up over and over. Learn them cold and you've secured a big share of your 40 correct answers.

The 7-step pre-trip inspection

Vehicle inspection is one of the biggest topic areas, and the 7-step method is its backbone. Know that inspection happens in three phases — pre-trip, en-route, and post-trip — and that the pre-trip follows a consistent 7-step order. Expect questions on what you check, when, and why.

The following distance rule

This is the single most testable number on the exam:

One second of following distance per 10 feet of vehicle length, at speeds under 40 mph. Add one second when you're going over 40 mph.

So a 60-foot rig needs about 7 seconds of following distance (6 seconds for the length + 1 for being above 40 mph). Practice applying it to different vehicle lengths and speeds.

Stopping distance

Total stopping distance is perception distance + reaction distance + braking distance. It grows with both speed and weight — a loaded truck at highway speed needs far more room than intuition suggests. Understand the three components and the fact that they compound.

Space management and hazard perception

The core domain is about seeing hazards early and managing the space around your vehicle — mirrors, signaling, adjusting speed, and leaving yourself an out. Think of every question here as: what does a professional do to stay safe before a problem develops?

ABS (anti-lock braking systems)

A classic trap. Know exactly what ABS does and doesn't do:

• ABS prevents wheel lock-up and helps you steer while braking hard
• ABS does NOT shorten your stopping distance — you still brake normally

Skids

Skids are caused by too much brake, too much steering, or too much gas. To recover, ease off whatever you're overdoing and steer into the direction of the skid.

Weight and balance

From the cargo section, know the three weight terms and how they differ:

• GVWR — gross vehicle weight rating
• GVW — gross vehicle weight (actual)
• GCWR — gross combination weight rating

Also understand axle and legal weight limits, center of gravity, and the principle to keep the load low and balanced to stay stable.

Memory aids

Short phrases beat long re-reading. Anchor these:

• "1 second per 10 feet, plus 1 above 40 mph." — following distance
• "ABS doesn't stop you shorter, it keeps you straight." — anti-lock braking
• "Get in the right gear BEFORE the downgrade." — mountain driving and control
• "3 skid causes = too much brake, steer, or gas." — skid recovery

A 1-2 week study plan

The GK test rewards focused, test-driven prep. Here's a schedule you can compress to one week or stretch to two.

Days 1-2: Read the core

Work through the "Driving Safely" section of your state's CDL manual, focusing on space and hazard management — the biggest topic area. Take notes on the following distance rule and stopping distance.

Days 3-4: Inspection + control

Learn the 7-step pre-trip inspection in order. Cover basic control and shifting. Start doing practice questions at the end of each session instead of just re-reading.

Days 5-6: Emergencies, conditions, and cargo

Cover ABS, skids, brake failure, and blowouts; adverse conditions (night, fog, winter, mountain, railroad crossings); and cargo, weight, and balance (GVWR/GVW/GCWR, securing loads, center of gravity).

Days 7+: Mixed practice until you're consistent

Switch entirely to full-length practice tests. Score 80% or better, consistently, before you book. For every question you miss, write one sentence on why the right answer is right — that's where the score gains come from. Repeat until 80% is your floor, not your ceiling.

Want questions to drill against? You can practice the CDL General Knowledge test on Cert Climb and see where you actually stand.

Frequently asked questions

What score do I need to pass the CDL General Knowledge test?

80% — typically 40 of 50 questions. This is a federal minimum, so no state can set it lower.

How many questions are on the test?

About 50 multiple-choice questions, drawn randomly from the model manual. Time limits vary by state, so check yours.

How much does it cost?

There's no separate GK fee. It's bundled into your permit and license fees, which vary by state — the CLP runs roughly $10-100 and total CDL licensing roughly $20-150.

What does passing unlock?

Passing gets you the Commercial Learner's Permit (CLP), which is valid 180 days (states may extend it up to a year). You must hold the CLP at least 14 days before you can take the CDL skills (road) test. Passing GK unlocks the permit, not the CDL — and endorsements are separate tests (more on that in our companion guide).

Verify your state

Because the GK test is administered by each state's DMV from the AAMVA model manual, the exact question count, time limit, and fees vary. Always confirm the details with FMCSA and your state's CDL manual before you schedule.

Ready to pass

The CDL General Knowledge test is very passable with a week or two of focused, question-driven prep. Learn the following distance rule, the 7-step inspection, how ABS and skids work, and the weight-and-balance basics, and you'll clear the 80% bar.

When you want to know you're ready, drill CDL General Knowledge questions on Cert Climb — and read the companion, How to Pass the CDL General Knowledge Test, for the fastest route in.