Your liver processes alcohol at a steady rate of about one standard drink per hour, lowering your blood alcohol concentration (BAC) by roughly .015 to .020 per hour. That means if you’re at the legal limit of .08 BAC, it takes four to five hours to reach zero. But “leaving your system” can mean different things depending on the type of test, and some markers of alcohol use stick around far longer than the buzz does.
What Counts as One Drink
The one-drink-per-hour rule only works if you know what a “standard drink” actually is. In the United States, one standard drink contains 0.6 ounces (14 grams) of pure alcohol. That translates to 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of 80-proof liquor. A generous home pour of whiskey or a strong cocktail can easily equal two standard drinks, which means the math doubles even if you only had “one glass.”
How Your Body Breaks Down Alcohol
Nearly all the alcohol you drink gets processed in the liver through a two-step chemical reaction. First, an enzyme converts ethanol into a toxic byproduct called acetaldehyde, which is a known carcinogen. A second enzyme then quickly converts acetaldehyde into acetate, a much less harmful substance that your body breaks down into water and carbon dioxide for easy elimination.
This process runs at a fixed speed. Coffee, cold showers, food after drinking, and exercise do nothing to accelerate it. Time is the only thing that clears alcohol from your body.
Estimated Clearance by Number of Drinks
Using the average metabolism rate of .015 to .020 BAC per hour, here’s a rough timeline for reaching a BAC of zero after your last sip:
- 1 standard drink: 1 to 2 hours
- 2 standard drinks: 2 to 3 hours
- 4 standard drinks: 4 to 6 hours
- 6 standard drinks: 7 to 10 hours
- 8 standard drinks: 10 to 13 hours
These are estimates for an average-weight adult. If you had a heavy night of drinking and stopped at midnight, your BAC might not hit zero until late the next morning or even the afternoon. Many people are still legally impaired when they drive to work the morning after a night out.
Detection Windows by Test Type
BAC reaching zero doesn’t mean every trace of alcohol is gone. Different tests look for different markers, and their detection windows vary dramatically.
Breath test: A breathalyzer can detect alcohol for up to 12 to 24 hours after your last drink, depending on how much you consumed. For moderate drinking, 12 hours is more typical. Heavier drinking pushes closer to 24.
Blood test: A standard blood alcohol test can detect alcohol for approximately 12 hours after your last drink.
Urine (standard): A basic urine test picks up alcohol for roughly 12 to 24 hours.
Urine (EtG test): This is the one that catches people off guard. EtG tests look for a specific metabolite your body produces when processing alcohol. After a few drinks, EtG can show up in urine for up to 48 hours. With heavier drinking, detection extends to 72 hours or longer.
Hair test: Hair follicle tests can detect alcohol use from one to six months after consumption. Because hair grows slowly and retains chemical markers, this test is used to identify patterns of drinking over time rather than a single episode.
Why Speed Varies From Person to Person
The one-drink-per-hour figure is an average. Several factors shift it in either direction.
Biological sex: Women generally reach higher BAC levels than men after consuming the same amount of alcohol, even at similar body weights. Men carry more body water and less body fat, which means alcohol gets diluted across a larger volume. Hormonal differences, particularly testosterone levels, also play a role in how efficiently the liver processes alcohol. The practical result is that women typically feel the effects more intensely and take longer to fully clear the same number of drinks.
Body weight and composition: A larger person with more lean body mass has a bigger volume for alcohol to distribute through, resulting in a lower peak BAC from the same amount of alcohol.
Food in your stomach: Eating before or while drinking slows the rate alcohol enters your bloodstream, which lowers your peak BAC. Solid meals are more effective than liquid ones at delaying absorption. On an empty stomach, liquor (like vodka with tonic) reaches peak blood alcohol in about 36 minutes. Wine takes closer to 54 minutes, and beer around 62 minutes. With a full meal, all of these are delayed significantly. Slower absorption doesn’t change the total amount of alcohol your liver has to process, but it does reduce the peak concentration your body has to handle at once.
Liver health: Chronic heavy drinking, liver disease, and certain medications can all reduce your liver’s processing capacity, making clearance take longer.
Age: Liver enzyme activity tends to decline with age, which means older adults generally metabolize alcohol more slowly than younger adults at the same weight.
Liquor vs. Beer and Wine
The type of alcohol you drink doesn’t change how fast your liver works, but it does affect how quickly alcohol hits your bloodstream. Research on fasting subjects found that vodka mixed with tonic produced peak BAC nearly 30 minutes faster than beer. Spirits are more concentrated, so the alcohol reaches your small intestine and enters your blood more rapidly. Once it’s in your system, though, your liver processes it at the same fixed rate regardless of whether it came from whiskey, wine, or a lager.
Where liquor gets tricky is portion size. It’s easy to underestimate how many standard drinks are in cocktails. A Long Island iced tea can contain four or more standard drinks in a single glass. If you’re trying to estimate your clearance time, count by standard drink equivalents rather than by number of glasses.