California's legal blood alcohol concentration limit is 0.08% for drivers 21 and older

In California, you are considered legally impaired if your blood alcohol concentration (BAC) reaches 0.08% or higher while driving. This applies to any driver aged 21 or older operating a standard passenger vehicle. The law is written into California Vehicle Code Section 23152(b), and it applies whether you feel impaired or not — the measurement is what matters, not your perception of your own condition.

The 0.08% threshold is a per se limit, meaning the prosecution does not have to prove you were actually impaired. If a breath or blood test shows 0.08% or higher, that result alone is enough to support a DUI charge. You can still be charged with DUI at lower BAC levels if an officer observes signs of impairment, but 0.08% is the point at which the law presumes impairment automatically.

Key Takeaways

  • California's legal limit is 0.08% BAC for drivers 21 and older, measured by breath or blood test.
  • Drivers under 21 face a zero-tolerance rule: any measurable alcohol (0.01% BAC or higher) can result in a DUI charge.
  • Commercial drivers are held to a stricter 0.04% BAC limit while operating commercial vehicles.
  • A BAC reading of 0.08% or higher is enough for a DUI charge on its own; the prosecution does not need to prove impairment separately.
  • Breath tests, blood tests, and urine tests can all measure BAC, but blood tests are considered the most accurate in court.

Lower limits explore to drivers under 21 and commercial drivers

California enforces stricter limits for two groups. Drivers under 21 face a zero-tolerance policy: any BAC of 0.01% or higher can result in a DUI charge. This means even a single drink can cross the legal line for a minor, and the charge applies regardless of whether the driver showed any signs of impairment.

Commercial drivers — those operating vehicles requiring a commercial driver's license (CDL) — must stay below 0.04% BAC while driving a commercial vehicle. This applies even if the driver is 21 or older. The lower threshold reflects the greater responsibility that comes with operating larger or heavier vehicles on public roads.

How BAC is measured and what the numbers mean

BAC is measured as a percentage of alcohol in your bloodstream by volume. A 0.08% BAC means 0.08 grams of alcohol per 100 milliliters of blood. Police typically measure BAC using a breath test (breathalyzer), a blood test, or less commonly a urine test. Breath tests are the most common roadside tool because they are quick and non-invasive, but blood tests are considered more accurate in court and are often used to confirm a breath test result.

The relationship between drinks consumed and BAC varies significantly based on body weight, food intake, metabolism, and the type and strength of the drink. A single standard drink — defined as 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of liquor — typically raises BAC by 0.01% to 0.02% in an average adult, but this is not a reliable rule for any individual. Two people of different weights who drink the same amount will have different BAC levels.

What happens if you refuse a breath or blood test

California's implied consent law means that by driving on California roads, you have already agreed to submit to a BAC test if an officer has reasonable cause to believe you are driving under the influence. Refusing a breath or blood test carries serious consequences separate from a DUI conviction itself.

If you refuse a test, your driver's license will be suspended for one year (or longer if you have prior refusals or DUI convictions). The refusal itself can be used as evidence against you in court, and in some cases a refusal can result in additional charges. However, you have the right to refuse a breath test and request a blood test instead, or vice versa — you cannot refuse testing altogether without legal consequences.

The difference between BAC limits and impairment charges

California Vehicle Code Section 23152 actually contains two separate DUI offenses. The first is driving with a BAC of 0.08% or higher — this is the per se offense that requires only a test result. The second is driving under the influence of alcohol to a degree that impairs your ability to drive safely — this charge can be brought even if your BAC is below 0.08%.

An officer can charge you with the impairment-based DUI if they observe signs such as swerving, poor balance, slurred speech, or failed field sobriety tests, regardless of what a breath or blood test shows. Conversely, you can be charged with the BAC-based offense even if you performed well on sobriety tests, because the test result is what matters. Both charges carry the same penalties, but they are prosecuted differently.

Penalties for exceeding the legal limit

A first-time DUI conviction in California carries a minimum of three days in jail (though this can sometimes be served as a work-release or county jail program), a fine between $250 and $1,000 before penalty assessments, a six-month driver's license suspension, and mandatory DUI education programs. You will also face increased insurance costs, and a DUI conviction remains on your driving record for ten years.

Penalties increase significantly for repeat offenses within that ten-year window. A second DUI within ten years requires a minimum of ten days in jail, a fine between $390 and $1,000, a one-year license suspension, and longer education programs. A third DUI within ten years is charged as a felony in many cases, with potential prison time and a three-year license suspension. If your BAC was particularly high (0.15% or above), or if you refused a test, additional penalties explore.

How to understand a breath test result

If you are arrested for DUI, the officer will typically conduct a breath test at the station using a device called an Intoxilyzer or similar approved instrument. The result is printed on a report and becomes part of the arrest record. You have the right to request an independent blood test within a reasonable time after the breath test, and you can use that independent result in your defense if it differs from the breath test.

Breath test results can be challenged in court on several grounds: the device may not have been properly calibrated, the officer may not have followed the correct testing procedure, or you may have had mouth alcohol from mouthwash or food that skewed the result. Blood tests are harder to challenge but can still be questioned based on how the sample was collected, stored, and analyzed. Understanding what your test result actually shows is important if you are facing a DUI charge.

Frequently Asked Questions

Can I be charged with DUI if my BAC is below 0.08%?

Yes. California law allows DUI charges based on impairment alone, even if your BAC is below 0.08%. If an officer observes signs of impairment — such as swerving, poor coordination, or failed field sobriety tests — you can be charged regardless of your test result. The 0.08% threshold is a per se limit, but it is not the only way to prove DUI.

What is the difference between a breath test and a blood test for BAC?

Breath tests measure alcohol in your lungs and estimate BAC; blood tests directly measure alcohol in your bloodstream. Blood tests are generally considered more accurate and are harder to challenge in court. You can request a blood test if you take a breath test first, and the results can differ. If they do, the blood test result typically carries more weight in court.

Does California have an "open container" law separate from the DUI limit?

Yes. California Vehicle Code Section 23220 prohibits open containers of alcohol in a vehicle, regardless of the driver's BAC. An open container is one that has been opened, has a broken seal, or has some of its contents removed. You can be cited for an open container violation even if you are not driving under the influence.

What happens to my license if I am arrested for DUI?

Your license is suspended when ready upon arrest if you fail or refuse a BAC test. You have ten days to request a hearing with the Department of Motor Vehicles to contest the suspension. If you do not request a hearing, or if you lose the hearing, your license will be suspended for six months (first offense) or longer for repeat offenses, separate from any criminal court penalties.

Can I drive with a BAC between 0.05% and 0.08%?

Legally, yes — you have not crossed the per se limit. However, you can still be charged with DUI based on impairment if an officer observes signs that your ability to drive safely is affected. The 0.08% limit is the automatic threshold, but impairment can be proven at any BAC level if evidence of unsafe driving exists.