Almost everyone starting out asks the same question in the wrong order. They pick the truck they want to drive, then try to work out the license. The classes are defined the other way round: by weight ratings and by what is in the vehicle.
Get the class right first, because it decides which knowledge tests you sit.
Class A: combination vehicles
A Class A CDL is generally used for combination vehicles, including tractor-trailers, when the gross combination weight rating is 26,001 pounds or more and the towed unit is over 10,000 pounds.
Two numbers have to be true at once, which is the part people miss. A heavy truck pulling a light trailer is not automatically Class A. The towed unit has to be over 10,000 pounds as well.
Class A drivers normally take General Knowledge, Combination Vehicles, and Air Brakes if the vehicle has them, plus the vehicle inspection, basic control and road test.
Class B: single heavy vehicles
A Class B CDL is generally used for a single commercial motor vehicle with a gross vehicle weight rating of 26,001 pounds or more, plus limited towing.
This is the class behind most straight trucks, dump trucks, box trucks, concrete mixers and large buses. It is one heavy unit rather than a tractor and a trailer.
Class B drivers normally take General Knowledge and Air Brakes if the vehicle has them, plus the inspection and driving tests. Combination Vehicles is not part of it, which is the main difference in study time between B and A.
Class C: passengers, school bus or placarded hazmat
A Class C CDL may apply when the vehicle does not meet the Class A or B weight definitions but is used for passengers, school bus operation, or placarded hazardous materials.
Class C is the one people overlook, because the vehicle can be small. What puts it in scope is the cargo or the passengers, not the weight.
The weight ratings, not the vehicle
Ratings are what the manufacturer says the vehicle is rated to weigh, not what it happens to weigh on the day. A half-empty truck is still rated at its rating. If you are deciding a class from how loaded something feels, you are using the wrong measure.
Already driving Class B and want Class A?
You do not start over. The gap is mostly Combination Vehicles plus the skills test in a combination vehicle, which is why the upgrade is treated separately from a first license.
Work out your class
Exact requirements, fees and the agency that issues your license all vary by state. Two things worth doing before you pay for anything:
- Use the CDL Selector to narrow the class and endorsements from a few questions about the vehicle and the work.
- Read the class breakdown for your state, which names your state agency and what it asks for.
When you know the class, you know the tests, and you can try a free practice test before buying any study material.