In the United States, you are legally considered drunk at a blood alcohol concentration (BAC) of 0.08%, the standard threshold for a DUI charge in all 50 states. But impairment starts well before that number, and how drunk you actually feel depends on a long list of biological factors that vary from person to person.
The Legal Line: 0.08% BAC
Every state sets 0.08% BAC as the legal limit for adult drivers. Cross that line and you can be charged with driving under the influence, regardless of whether you feel impaired. For commercial drivers, the limit drops to 0.04%. For anyone under 21, most states enforce zero-tolerance laws with thresholds as low as 0.00% to 0.02%.
It’s worth noting that you can still face legal consequences below 0.08%. Many states have lesser charges for drivers at 0.05% or above who show signs of impairment. Utah is the strictest, with a legal limit of 0.05% for all adult drivers. If police pull you over and observe impaired behavior, your BAC reading is only one piece of the picture.
What Happens at Each BAC Level
Alcohol affects your brain in a predictable, dose-dependent way. Here’s what each BAC range typically looks like:
- 0.02%: Altered mood, slight relaxation, and a minor dip in judgment. Most people feel barely affected, but measurable changes in brain function are already underway.
- 0.05%: You feel uninhibited. Alertness drops and judgment becomes noticeably impaired. This is roughly where two drinks in an hour lands many people.
- 0.08%: Muscle coordination declines, it becomes harder to detect danger, and reasoning is clearly impaired. This is the legal limit, and reaction time is significantly slower.
- 0.15%: Nausea, vomiting, and loss of balance set in. Mood swings become more dramatic and muscle control deteriorates.
- 0.15% to 0.30%: Confusion, drowsiness, and vomiting. At the higher end, loss of consciousness is likely.
- 0.30% to 0.40%: This range constitutes alcohol poisoning. Loss of consciousness is expected, and the situation is life-threatening.
- Above 0.40%: Risk of coma and death from the body simply stopping breathing.
How “Drunk” You Feel Doesn’t Match Your BAC
One of the trickiest things about alcohol is the gap between how impaired you feel and how impaired you actually are. A 2024 study tracking young adults’ drinking in real time found that the correlation between subjective intoxication and actual blood alcohol levels varied wildly, not just between people but even for the same person on different days. On some occasions the two tracked closely; on others, someone’s self-rated intoxication barely correlated with their measured alcohol level at all.
The study also found that being “out” (at a bar, party, or social event) weakened the connection further. In other words, the environment makes you a worse judge of your own intoxication. The social energy, loud music, and stimulation mask the sedating effects of alcohol, so you feel more sober than you are. Interestingly, how drunk someone felt was actually a better predictor of next-morning consequences (headache, regret, poor decisions) than their measured BAC. Your brain’s subjective read matters, but it’s unreliable as a gauge of whether you’re safe to drive.
What Counts as One Drink
A standard drink in the United States contains 0.6 ounces (14 grams) of pure alcohol. That translates to:
- Beer: 12 ounces at 5% ABV
- Wine: 5 ounces at 12% ABV
- Liquor: 1.5 ounces (one shot) at 40% ABV (80 proof)
- Malt liquor: 8 ounces at 7% ABV
These are smaller than what most people pour. A typical restaurant wine glass holds 8 to 10 ounces, which is nearly two standard drinks. A pint of craft beer at 7% or 8% ABV can equal close to two drinks as well. If you’re trying to estimate your BAC, the real pour size matters more than the number of “drinks” you’ve had.
Why the Same Amount of Alcohol Hits People Differently
Two people can drink the exact same amount and end up at very different BAC levels. The biggest factors are body composition, sex, food intake, and medications.
Body composition plays a major role because alcohol dissolves in water, not fat. A person with more body fat and less body water will concentrate the alcohol into a smaller volume, pushing BAC higher. This is one reason women generally reach higher peak BAC levels than men given the same dose per kilogram of body weight: women on average carry a higher proportion of body fat. Men also appear to break down more alcohol in the stomach before it reaches the bloodstream, which further widens the gap.
Eating before or while drinking is the single most effective way to slow alcohol absorption. Food in the stomach delays alcohol from passing into the small intestine, where absorption is fastest. On an empty stomach, alcohol moves rapidly into the intestine, and peak BAC arrives sooner and higher. The old advice to never drink on an empty stomach is backed by solid physiology.
Certain medications also change the equation. Common heartburn drugs and aspirin can interfere with the stomach’s ability to break down alcohol, effectively raising your BAC from the same number of drinks. Other medications compete with alcohol for the same processing pathways in the liver, which can slow both alcohol elimination and the drug’s own metabolism, amplifying the effects of both.
How Police Measure Impairment
Beyond the breathalyzer, law enforcement relies on three standardized field sobriety tests validated by the National Highway Traffic Safety Administration. These are designed to detect physical impairment even when a precise BAC reading isn’t available.
The first is a test where an officer tracks your eye movements with a stimulus like a pen or small light. At certain BAC levels, the eyes begin to jerk involuntarily when looking to the side, a response you can’t fake or suppress. The second is a walk-and-turn test: nine heel-to-toe steps along a line, a turn, and nine steps back, all while listening to instructions. It tests your ability to divide attention between a physical and mental task. The third is a one-leg stand, where you balance on one foot for 30 seconds while counting aloud. Together, these three tests assess coordination, balance, and the ability to follow multi-step directions, all of which deteriorate reliably as BAC rises.
When Drinking Becomes a Medical Emergency
Alcohol overdose occurs when there’s enough alcohol in the bloodstream that the brain regions controlling breathing, heart rate, and temperature regulation begin to shut down. The warning signs include confusion or stupor, inability to stay conscious or be woken up, vomiting, seizures, breathing slower than 8 breaths per minute, gaps of 10 seconds or more between breaths, clammy skin, bluish skin color, and an extremely low body temperature.
One particularly dangerous sign is the loss of the gag reflex. This means someone who vomits while unconscious can choke without their body’s normal protective response kicking in. There is no single BAC that guarantees alcohol poisoning. Age, tolerance, speed of drinking, sex, body size, and medications all shift the threshold. BAC levels between 0.30% and 0.40% are where alcohol poisoning typically occurs, but for some people it can happen lower.
Binge drinking, defined as a pattern that brings BAC to 0.08% or above, is the most common pathway to alcohol overdose. For most women, that’s about four drinks in two hours; for most men, about five.