Use this guide to review California BAC thresholds by driver type and age, along with the important distinction between a legal threshold and whether a person is actually safe to drive.
QUICK ANSWER
California's illegal BAC threshold depends on the driver. The handbook lists 0.08% or higher for drivers over 21, 0.01% or higher for drivers under 21, 0.01% or higher at any age while on DUI probation, and 0.04% or higher for drivers operating a vehicle that requires a commercial license or carrying passengers for hire. A BAC below those limits does not automatically mean a person is safe to drive.
STUDY NOTES
BAC is not a safety target
The legal threshold is not a recommendation for how much someone can safely drink. DMV warns that alcohol can impair driving below the listed illegal BAC limits and that a driver may still be arrested and convicted of DUI based on impairment even without a BAC measurement.
Open containers
The handbook says alcohol or cannabis containers carried in a vehicle generally must be sealed and unopened. An opened alcohol container must be kept in the trunk or another area where passengers do not sit, and it may not be kept in the glove box. Specific passenger-vehicle exceptions are listed by DMV.
Chemical testing and DUI consequences
Driving in California carries implied-consent consequences. DMV explains that refusing a required breath, blood, or urine test can result in suspension or revocation of driving privileges. DUI convictions can also lead to license action, required programs, insurance filings, fees, and other penalties.
PRACTICE CHECKS
Check your understanding
Answer each question before opening the explanation.
1. What BAC level is illegal for a driver under 21?
Show answer
Answer: 0.01% or higher.
California's under-21 rule is stricter than the 0.08% threshold listed for drivers over 21.
2. What BAC level is illegal for a driver over 21?
Show answer
Answer: 0.08% or higher.
The handbook lists 0.08% as the illegal threshold for drivers over 21.
3. Does a BAC below the legal limit guarantee that you are safe to drive?
Show answer
Answer: No.
DMV warns that alcohol can negatively affect driving below the listed illegal BAC limits.
FAQ
Common questions
What is the California BAC limit for drivers under 21?
The California Driver's Handbook lists 0.01% or higher as illegal for drivers under 21.
What is the BAC limit while on DUI probation?
The handbook lists 0.01% or higher at any age while on DUI probation.
What is the BAC limit for a commercial driver?
DMV lists 0.04% or higher for a driver operating a vehicle that requires a commercial driver's license.
Can I be impaired below 0.08%?
Yes. DMV states that alcohol can negatively affect driving below the illegal BAC limits and that impairment can still lead to DUI consequences.
VERIFY THE RULE
Official source
This study page was reviewed against the DMV material below. Open the source when you want the complete rule, exceptions, or surrounding context.
Last reviewed: August 16, 2026 · Reviewed by Master My Test