Your body clears alcohol at a fairly fixed rate of about one standard drink per hour. If you’ve had four drinks, expect roughly four to five hours before your blood alcohol level returns to zero. But reaching a 0.00 reading doesn’t necessarily mean you feel or perform normally, and several factors can shift that timeline in either direction.
The Basic Math of Alcohol Processing
Your liver does nearly all the work of breaking down alcohol, and it operates at a steady pace that you can’t speed up. The average person’s blood alcohol concentration drops by about 0.015 to 0.020 percent per hour. In more concrete terms, that’s roughly one standard drink (a 12-ounce beer, a 5-ounce glass of wine, or a 1.5-ounce shot of liquor) every 60 minutes.
This means someone right at the legal driving limit of 0.08 percent BAC would need four to five hours to reach 0.00. Someone who drinks heavily and reaches a BAC of 0.15 could need 10 hours. A study of over 100 intoxicated emergency department patients, who arrived with an average blood alcohol level of 0.30 percent (nearly four times the legal limit), found their bodies cleared alcohol at an average rate of about 20 mg/dL per hour. At that rate, reaching zero from 0.30 would take roughly 15 hours.
The critical thing to understand is that this rate is essentially constant. Your liver processes alcohol at the same pace whether you’ve had two drinks or ten. More drinks simply means a longer wait, not a faster metabolism.
Why Your Timeline May Differ From Someone Else’s
While one drink per hour is a useful rule of thumb, individual variation is real. That same emergency department study found a standard deviation of about 6 mg/dL per hour, meaning some people cleared alcohol nearly twice as fast as others. Several biological factors explain the range.
Body size and composition. Alcohol dissolves in water, and your body’s water content determines how concentrated it becomes in your blood. A larger person with more lean body mass dilutes the same number of drinks across a bigger volume, reaching a lower peak BAC and returning to zero sooner. Women generally have a lower proportion of body water than men of similar weight, which means the same number of drinks produces a higher blood alcohol concentration.
Sex differences in metabolism. Beyond body water, liver volume matters. Research using intravenous alcohol (which bypasses the stomach and isolates liver function) found that women had approximately 27 percent lower alcohol elimination rates than men. The difference was largely explained by smaller lean body mass and liver volume rather than by sex alone.
Age. As you get older, the enzymes responsible for breaking down alcohol become less active, and your body’s water volume shrinks. Both changes mean older adults reach higher blood alcohol levels from the same amount of alcohol and take longer to clear it. The brain and liver also become more sensitive to alcohol’s toxic effects with age, so the same BAC can produce more impairment.
Genetics. Certain gene variants significantly affect how fast your body converts alcohol. People of East Asian descent frequently carry a variant of an enzyme that processes alcohol’s toxic byproduct (acetaldehyde) very slowly, causing intense flushing, nausea, and discomfort even from small amounts. On the other end, some genetic variants common in people of African ancestry are associated with faster alcohol elimination. These genetic differences influence not just how quickly you sober up but also how unpleasant the experience feels along the way.
Nothing Speeds Up the Process
Coffee, cold showers, exercise, greasy food, energy drinks: none of these change how fast your liver metabolizes alcohol. Studies have directly tested whether adding energy drinks to alcohol alters breath alcohol concentrations, and it doesn’t. Caffeine can make you feel more alert, which creates a dangerous illusion of sobriety while your BAC remains unchanged. Your liver clears alcohol between 15 and 20 mg percent per hour regardless of what else you consume or do. Time is the only thing that works.
Sober on Paper vs. Actually Sober
Here’s something most people don’t realize: your blood alcohol can hit 0.00 and you can still be meaningfully impaired. The alcohol hangover, by definition, begins as blood alcohol approaches zero. It’s not just a headache. A meta-analysis of 19 studies found that sustained attention, short- and long-term memory, and reaction speed are all degraded during a hangover.
The practical consequences are significant. Research has shown that hangover-related driving impairment is comparable to driving with a BAC of 0.05 to 0.08 percent, which is at or above the legal limit in most countries. Working memory and executive function (your ability to plan, make decisions, and switch between tasks) decline in proportion to hangover severity. So even after the alcohol itself is gone, the cognitive aftermath can linger for hours.
This means the real answer to “how long until I’m sober” is longer than simple BAC math suggests. If you drank heavily the night before and your BAC returns to zero by 6 a.m., you may still be functionally impaired at 9 or 10 a.m.
Rough Timelines by Number of Drinks
These estimates assume an average-sized adult and a clearance rate of 0.015 percent BAC per hour. Your individual timeline could be shorter or longer based on the factors above.
- 2 standard drinks: approximately 2 to 3 hours to reach 0.00 BAC
- 4 standard drinks: approximately 4 to 6 hours
- 6 standard drinks: approximately 7 to 9 hours
- 8 standard drinks: approximately 9 to 12 hours
- 10 or more standard drinks: 12 hours or longer
Add a few more hours on top of these estimates if you want to account for hangover-related impairment after a heavy session. If you had a big night and need to drive the next morning, a personal breathalyzer can give you a reading, though keep in mind that breathalyzers tend to read slightly lower than actual blood alcohol levels. In one study comparing 404 paired breath and blood samples, the breathalyzer result was lower than the blood result by more than 0.01 percent about 61 percent of the time. A reading of 0.00 on a consumer breathalyzer is encouraging, but it doesn’t guarantee your cognitive performance is back to baseline.
What Actually Helps
Since you can’t accelerate the process, the only practical strategies involve giving your body enough time and supporting it while it works. Drinking water between alcoholic drinks and before bed helps with dehydration symptoms but won’t lower your BAC faster. Eating before or while you drink can slow alcohol absorption into your bloodstream, which means a lower peak BAC to begin with, giving your liver less total work to do. Sleep gives your body uninterrupted hours to process what’s in your system.
The most effective approach is simply planning ahead. Count your drinks, note what time you stopped, and add roughly one hour per drink plus a buffer for hangover effects. If you’re trying to be safe to drive by morning, finishing your last drink earlier in the evening is the only reliable way to make that happen.