Blood alcohol limits — California Permit Test

Blood alcohol limits on the California permit test — 7 rules, each with the reason behind it and a question on it while it is fresh.

The rules

It is illegal to drive if you have a blood alcohol concentration of 0.08% or higher and you are over 21 years old.

It is the line the state draws for an adult, and a breath test settles which side you are on.

It is illegal for you to drive if you have a BAC of:
California Driver’s Handbook, p.73

It is illegal to drive if you have a blood alcohol concentration of 0.01% or higher and you are under 21 years old.

For a driver under 21 the limit is effectively nothing at all.

0.01% or higher if you are under 21 years old.
California Driver’s Handbook, p.73

It is illegal to drive at any age with a blood alcohol concentration of 0.01% or higher if you are on DUI probation.

Probation replaces the adult limit with the same one a teenager gets, whatever your age.

0.01% or higher at any age if you are on DUI probation.
California Driver’s Handbook, p.73

It is illegal to drive a vehicle that requires a commercial driver’s license, or to drive a passenger for hire, with a blood alcohol concentration of 0.04% or higher.

A commercial driver is responsible for a far heavier vehicle or for the people in it.

0.04% or higher if you drive a vehicle that requires a commercial driver’s license.
California Driver’s Handbook, p.73

Even if your blood alcohol is below the legal limits, that does not mean it is safe for you to drive, and you may be arrested and convicted of a DUI without a blood alcohol measurement at all.

The offense is being impaired. The number is only one way of proving it.

Even if your BAC is below legal limits, that does not mean it is safe for you to drive.
California Driver’s Handbook, p.73

Almost everyone feels negative effects of alcohol even at levels lower than the legal limit, and even one drink can affect your ability to drive safely.

The first drink is already doing something, and the limit is not where the effect starts.

Almost everyone feels negative effects of alcohol,
California Driver’s Handbook, p.73

It is illegal to drink alcohol or take drugs when you are operating a boat, jet ski, water skis, aquaplane or similar vessel.

The same impairment matters on the water, and the same law reaches it.

NOTE: It is illegal to drink alcohol or take drugs when you are operating a boat, jet ski, water skis, aquaplane, or similar vessels.
California Driver’s Handbook, p.73

On the test

What is the blood alcohol limit for a driver over 21?

A BAC of 0.08%. It is the line the state draws for an adult, and a breath test settles which side you are on. California Driver’s Handbook, p.73: “It is illegal for you to drive if you have a BAC of:”

How this works

Most practice tests hand you a bank of questions and leave the manual somewhere else. This one puts them together.

You read one law and the reason behind it, then answer a question on that law while it is still fresh. Get it right and you move on; get it wrong and you have found the gap while it is cheap to fix, not on the morning of the exam.

Learning one rule at a time, and proving it immediately, is what turns a manual you skimmed into something you actually know — and it makes studying feel like getting somewhere rather than like waiting to find out.

What it costs

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Where these come from

Every rule here is checked against California Driver’s Handbook, published by the California Department of Motor Vehicles, and against the state code itself. Last checked 2026-09-21.