The legal drinking and driving limit in the United States is 0.08% blood alcohol concentration (BAC) for most adult drivers, with Utah the sole exception at 0.05%. Commercial drivers are limited to 0.04%, and drivers under 21 face zero tolerance laws that set the ceiling at 0.02% or lower. Hitting or exceeding your category’s threshold is enough to be charged, whether or not you feel impaired.
The 0.08% Standard for Adult Drivers
Every state treats 0.08% BAC as the line where an adult driver is legally intoxicated. This is a “per se” standard: the number by itself is enough to convict. Prosecutors don’t need to show you were swerving, slurring, or driving badly. If your chemical test comes back at 0.08% or above, the law considers you impaired.1National Highway Traffic Safety Administration. 0.08 BAC Sanction
Utah broke from the pack in 2018 by lowering its per se limit to 0.05%, and it remains the only state to do so. NHTSA research has since found the lower limit showed promise in reducing impaired driving, and the agency has positioned Utah as a potential model for other states.2National Highway Traffic Safety Administration. Utah’s .05% Law Shows Promise to Save Lives, Improve Road Safety
One point that catches people off guard: you can still be charged with impaired driving at a BAC below 0.08%. If an officer observes signs of impairment and you blow a 0.06%, most states allow prosecutors to pursue charges based on the totality of the evidence. The 0.08% threshold simply removes the need to prove impairment through behavior.
What 0.08% Looks Like in Drinks
BAC measures grams of alcohol per deciliter of blood. The number most people actually want to know is how many drinks it takes to get there. A “standard drink” contains about 0.6 fluid ounces of pure alcohol, which translates to roughly 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of liquor.3Centers for Disease Control and Prevention. Impaired Driving
How quickly those drinks push you to 0.08% depends on your weight, biological sex, how fast you’re drinking, and whether you’ve eaten. A 140-pound man might reach 0.08% after roughly three standard drinks in an hour. A 140-pound woman could reach it after two. Larger people generally need more alcohol to hit the same BAC, but the math is unreliable enough that counting drinks is a poor substitute for not driving. Your body metabolizes about 0.015% BAC per hour, so time between drinks matters, but the rate is slow enough that a heavy evening can leave you over the limit well into the next morning.
Impairment itself starts well before the legal limit. Reaction time, coordination, and judgment all degrade at BAC levels as low as 0.02% to 0.05%. The 0.08% threshold isn’t the point where alcohol starts affecting your driving; it’s the point where the law draws a bright line.
The 0.04% Limit for Commercial Drivers
If you hold a commercial driver’s license (CDL), the legal limit drops to 0.04% BAC. Federal regulations prohibit any CDL holder from reporting for duty or remaining on duty while performing safety-sensitive functions at or above that level.4eCFR. 49 CFR Part 382 – Controlled Substances and Alcohol Use and Testing
The stakes for commercial drivers go beyond a traffic ticket. A first alcohol-related conviction while operating a commercial vehicle triggers a one-year disqualification from holding a CDL. A second conviction in a separate incident results in a lifetime disqualification. The same lifetime ban applies if the second offense involves refusing an alcohol test, leaving an accident scene, or causing a fatality through negligent driving.5eCFR. 49 CFR 383.51 – Disqualification of Drivers
A lifetime disqualification isn’t always permanent. After 10 years, a state may reinstate a driver who has completed an approved rehabilitation program. But if that driver picks up another qualifying offense after reinstatement, the disqualification becomes permanent with no second chance.5eCFR. 49 CFR 383.51 – Disqualification of Drivers
Zero Tolerance for Drivers Under 21
Drivers under 21 face what are commonly called zero tolerance laws. Because alcohol is illegal for minors to purchase or possess, the legal BAC limit for underage drivers drops to 0.02% or lower, depending on the state. Some states set the bar at 0.00%, meaning any detectable alcohol triggers a violation.
The 0.02% threshold most states use isn’t a concession that a little drinking is acceptable. It exists to account for trace amounts of alcohol that might show up from mouthwash, cold medicine, or testing equipment tolerances. In practice, even one beer puts most young drivers over 0.02%. Consequences for underage violations are typically administrative rather than criminal for a first offense, but they still include license suspension and can appear on a driving record.
Enhanced Penalties for High BAC
Blowing a 0.08% and blowing a 0.18% are not treated the same way. The vast majority of states impose escalated penalties when a driver’s BAC significantly exceeds the standard limit. The most common trigger points are 0.15% and 0.16%, though some states set the bar at 0.17%, 0.18%, or 0.20%. A handful of states have multiple tiers with increasing penalties at each threshold.
These aggravated or “high BAC” charges carry stiffer consequences at every level: longer license suspensions, higher minimum fines, mandatory minimum jail sentences that might not apply to a standard first offense, and a greater likelihood that the court will order an ignition interlock device. In states with tiered systems, a BAC above 0.20% can mean penalties approaching those of a second or third offense even on a first arrest. Aggravated charges also often come with mandatory alcohol treatment programs, extended probation, and surcharges a standard DUI might not trigger.
Drug-Impaired Driving
There is no single national BAC-style limit for drug-impaired driving. States take three different approaches, and where you’re driving determines which rules apply.
A handful of states have adopted per se THC limits, making it illegal to drive with a specific concentration of tetrahydrocannabinol in your blood. Washington, for instance, sets the threshold at 5 nanograms per milliliter. Colorado uses a different framework: 5 ng/ml of THC creates a “permissible inference” of impairment, but it isn’t automatic proof the way a 0.08% BAC is for alcohol, and a driver can still argue they weren’t actually impaired.6National Highway Traffic Safety Administration. Drug-Impaired-Driving Laws
About a dozen states take a zero tolerance approach, making it illegal to drive with any detectable amount of THC or other controlled substances in your system. Because THC metabolites can linger in blood for days or weeks after the psychoactive effects have worn off, a person who used marijuana days earlier and is completely sober can still test positive and face charges.
Where no specific chemical threshold exists for a drug, prosecutors must prove impairment through behavioral evidence: field sobriety tests, officer observations, and testimony from drug recognition experts. This impairment-based approach is harder to prosecute but applies to any substance, including prescription medications that affect driving ability.
Implied Consent and Refusing a Test
Every state has an implied consent law. The basic principle is that by driving on public roads, you’ve already agreed to submit to a chemical test if lawfully arrested on suspicion of impaired driving. This isn’t optional consent you can revoke without consequences.
Refusing the post-arrest chemical test triggers automatic administrative penalties, regardless of whether you were actually impaired. The most common consequence is a license suspension lasting 12 months for a first refusal, with longer suspensions for repeat refusals. In many states, the refusal itself can also be introduced as evidence against you at trial, creating an inference that you refused because you knew you’d fail.
Federal law reinforces this framework. Under 23 U.S.C. ยง 164, Congress requires states to treat a test refusal by a repeat offender the same as a conviction when determining penalties, including mandatory license suspension or ignition interlock installation.7Office of the Law Revision Counsel. 23 US Code 164 – Minimum Penalties for Repeat Offenders for Driving While Intoxicated or Driving Under the Influence
Note that the handheld roadside breath test an officer may ask you to blow into during a traffic stop is a separate thing from the formal post-arrest chemical test. Refusing the roadside preliminary screening carries minor or no administrative penalties in most states. Implied consent applies to the evidentiary test given after a lawful arrest.
Penalties for Going Over the Limit
A first-offense DUI is a misdemeanor in every state, but “misdemeanor” understates what it costs. Statutory fines for a first conviction typically range from $1,000 to $4,000 before court costs, assessments, and surcharges push the total higher. Most states authorize jail sentences of up to six months or a year for a first offense, though many first-time offenders receive probation instead. License suspensions for a first conviction commonly last 90 days to one year.
Repeat offenses escalate sharply. Federal law pushes states to impose minimum penalties on second and subsequent offenders, including at least a one-year license suspension or ignition interlock requirement, an alcohol abuse assessment, and either five days of jail or 30 days of community service for a second offense. Third offenses require at least 10 days of jail or 60 days of community service.7Office of the Law Revision Counsel. 23 US Code 164 – Minimum Penalties for Repeat Offenders for Driving While Intoxicated or Driving Under the Influence
Certain circumstances elevate a DUI from a misdemeanor to a felony. The most common triggers are multiple prior convictions within a lookback period, causing serious injury or death while driving impaired, and driving drunk with a child in the vehicle. Felony DUI convictions carry prison sentences measured in years rather than months, along with fines that can reach $10,000 or more.
Costs That Outlast the Sentence
The sentence a judge hands down is only the start. Several ongoing obligations follow a DUI conviction, each with its own cost and timeline.
Ignition Interlock Devices
An ignition interlock device is a breath-testing unit wired into your vehicle’s starter. You blow into it before the car will start, and it requires periodic retests while you’re driving. Thirty-one states and the District of Columbia now require these devices for all offenders, including first-timers. Other states reserve the requirement for high-BAC offenders or repeat offenders, and a few leave it to judicial discretion. Installation typically costs $75 to $200, with monthly lease and calibration fees running $70 to $100. Most states require the device for at least six months on a first offense, and longer for repeat convictions.
SR-22 Insurance Filing
After a DUI-related license suspension, most states require you to carry an SR-22 filing before your license can be reinstated. An SR-22 isn’t a separate insurance policy. It’s a certificate your insurer files with the state confirming you carry at least the minimum required liability coverage. The filing requirement lasts three years in most states, and any lapse in coverage during that period can reset the clock and delay reinstatement.
Insurance Rate Increases
A DUI conviction stays on your driving record for years, and insurers treat it as a major risk factor. The practical result is that your auto insurance premiums will roughly double. That increase persists for three to five years in most states and can add thousands of dollars on top of fines, legal fees, and device expenses. When people say a DUI costs $10,000 or more in total, the insurance increase is often the single largest component.