In 49 states and Washington, D.C., the legal BAC limit to drive is 0.08% for anyone 21 or older. Utah sets it at 0.05%. Commercial drivers face a 0.04% ceiling nationwide, and drivers under 21 are held to near-zero limits in every state. Those numbers are the “per se” thresholds — hit them and you’re legally drunk by definition — but you can be arrested and convicted at a lower BAC if an officer concludes alcohol has impaired your driving.
The Per Se Limits by Driver Type
Blood alcohol content measures the percentage of alcohol in your bloodstream. Every state treats a BAC at or above its per se limit as an automatic violation. Prosecutors don’t need to prove you were swerving or slurring; the number alone establishes the offense. Congress effectively standardized 0.08% nationwide by threatening to withhold highway construction funding from any state that didn’t adopt it.1National Highway Traffic Safety Administration. 0.08 BAC Sanction FAQ
Utah broke from that standard in 2018, dropping its per se limit to 0.05%, the lowest in the country.2Utah Highway Safety. Utah’s 0.05 BAC Law No other state has followed.
Two groups of drivers face tighter limits everywhere:
- Commercial drivers are capped at 0.04% BAC when operating a commercial motor vehicle, and that limit applies regardless of whether they’re on or off duty at the time of the stop.3Federal Motor Carrier Safety Administration. Is a Driver Disqualified for Driving a CMV While Off-Duty with a Blood Alcohol Concentration Over 0.04 Percent
- Drivers under 21 are subject to zero-tolerance laws nationwide, which set the threshold at 0.02% or 0.00% depending on the state. Congress tied these laws to federal highway funding, making adoption effectively mandatory.
You Can Be Arrested Below the Per Se Limit
The 0.08% number (0.05% in Utah) is the level at which impairment is legally presumed. It is not a safe harbor. Every state also has impairment-based drunk driving laws that let officers charge you at any BAC — 0.04%, 0.05%, 0.06% — if your driving, speech, coordination, or behavior shows that alcohol has affected your ability to operate a vehicle safely.
A driver who blows 0.06% can still be arrested and convicted if the officer documents enough evidence: failed field sobriety tests, weaving between lanes, slow reactions at intersections. The per se limit makes the prosecutor’s job easier. It isn’t the only route to a conviction.
Impairment also begins well before 0.08%. The National Highway Traffic Safety Administration reports measurable effects on judgment and object tracking at 0.02%, and noticeably reduced coordination, steering control, and emergency response at 0.05%.4National Highway Traffic Safety Administration. The ABCs of BAC The legal line at 0.08% doesn’t mark the start of impairment; it’s where legislators decided the risk was undeniable enough to presume it automatically.
How Many Drinks Reach the Limit
Most people underestimate how much they’ve had because they don’t know what a standard drink is. The National Institute on Alcohol Abuse and Alcoholism defines one standard drink as any beverage containing 0.6 fluid ounces (14 grams) of pure alcohol.5National Institute on Alcohol Abuse and Alcoholism. What Is a Standard Drink? That works out to:
- 12 ounces of beer at about 5% alcohol
- 5 ounces of wine at about 12% alcohol
- 1.5 ounces of distilled spirits (a standard shot) at about 40% alcohol
The math catches people off guard. A 16-ounce craft IPA at 7.5% alcohol is roughly two standard drinks, not one. A generous restaurant pour of wine can easily hit 8 ounces, which is over one and a half standard drinks. Mixed cocktails at bars routinely contain two or three shots. Counting by the glass almost always undercounts.
What Changes Your BAC
Two people can drink the same amount and register very different BAC readings. The biggest variables are body weight and composition. Alcohol distributes through the body’s water content, so a smaller person with less total body water reaches a higher BAC from the same number of drinks. Women typically reach higher BAC levels than men of the same weight because they carry proportionally less body water and produce less of the enzyme that breaks down alcohol in the stomach.
Food matters. Drinking on an empty stomach sends alcohol into your bloodstream fast and produces a sharp BAC spike. Eating before or while drinking slows absorption and keeps the peak lower. Pace matters too. Three drinks in one hour produces a far higher BAC than three drinks across three hours, because the body only processes alcohol so quickly.
Your liver clears alcohol at roughly 0.015% BAC per hour, regardless of size or sex. Nothing speeds that rate up. Not coffee, not a cold shower, not exercise. If you stop drinking at a BAC of 0.08%, it takes more than five hours to reach 0.00%. Morning-after DUI arrests happen all the time because drivers assume they’ve slept it off when their BAC is still above the legal limit.
What Happens If You’re Tested
Every state has an implied consent law. When you get your driver’s license, you automatically agree to submit to a chemical BAC test — breath, blood, or urine — if you’re lawfully arrested on suspicion of drunk driving. You can refuse, but refusal carries its own penalties that are often as bad as or worse than failing the test. Most states impose an automatic license suspension for refusal, typically longer than the suspension for a failed test, and prosecutors can use the refusal as evidence against you at trial.
There are constitutional limits. The U.S. Supreme Court ruled in 2016 that states can require breath tests without a warrant as part of a drunk driving arrest, but they cannot require warrantless blood draws. A state can impose civil penalties for refusing a blood test. It cannot make refusal a criminal offense on its own.6Justia US Supreme Court. Birchfield v. North Dakota, 579 U.S. ___ (2016) If police want a blood sample and you refuse, they’ll usually get a warrant, and modern procedures make that fast enough that refusal rarely stops the test from happening.
What a Conviction Costs
Penalties vary by state, but the landscape is consistent because Congress requires states to maintain minimum penalties for repeat offenders as a condition of federal highway funding.7Office of the Law Revision Counsel. 23 USC 164 – Minimum Penalties for Repeat Offenders for Driving While Intoxicated or Driving Under the Influence
License Suspension and Ignition Interlock
A first-offense conviction typically brings a license suspension of 30 days to one year, depending on the state and your BAC at the time of arrest. Over 30 states now require first-time offenders to install an ignition interlock device, a breathalyzer wired to the ignition that prevents the engine from starting if it detects alcohol. You pay for the device, the installation, and a monthly monitoring fee, generally several hundred dollars over the required period.
Federal law sets a floor for second offenses: at least one year of full suspension, restricted driving with an interlock, participation in a 24/7 sobriety program, or a combination. Most states exceed that minimum. A third or subsequent offense carries longer suspensions and mandatory jail time or community service.
Fines, Fees, and Insurance
A first-offense fine commonly starts around $500 to $1,000. The real cost climbs quickly once you add court costs, administrative fees, mandatory alcohol education classes, license reinstatement fees of roughly $100 to $500, and any required substance abuse evaluation. Industry estimates put the total financial hit of a first DUI at roughly $10,000 once attorney fees, higher insurance premiums, and lost work time are factored in.
Insurance is where the costs compound longest. After a DUI, most states require you to file an SR-22 or similar proof of financial responsibility, which flags you as a high-risk driver. Premiums roughly double on average, and that increase typically lasts three to five years or longer. Over that span, the added insurance cost alone can exceed every other DUI expense combined.
High-BAC and Felony Escalators
Most states impose harsher penalties when your BAC significantly exceeds the per se limit. The most common threshold for these “aggravated” or “extreme” DUI charges is 0.15%, though some states draw the line at 0.16%, 0.17%, or as high as 0.20%. Enhanced penalties can include higher minimum fines, longer license suspensions, mandatory jail time even for a first offense, and extended interlock requirements.
A first-offense DUI is typically a misdemeanor. It escalates to a felony under several circumstances that recur across states:
- Most states elevate the charge to a felony after three or four convictions within a specified lookback period, which varies from five years to a lifetime depending on the state.
- Drunk driving that causes serious bodily injury or death is charged as a felony in every state, often carrying prison sentences measured in years rather than months.
- Many states treat driving drunk with a minor in the vehicle as an automatic aggravating factor that can elevate the charge.
A felony DUI conviction carries consequences that outlast the sentence: effects on employment, housing, professional licensing, and the right to own firearms long after the legal case closes.