Your liver processes roughly one standard drink per hour, lowering your blood alcohol concentration (BAC) at a fairly steady rate of about 0.015 per hour. That means if you stop drinking at a BAC of 0.08 (the legal limit in most U.S. states), it takes around five to six hours to reach zero. But “leaving your system” can mean different things depending on the type of test, and several personal factors speed up or slow down the process.
The One-Drink-Per-Hour Rule
A standard drink is 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of liquor. Your liver handles about one of these per hour. Unlike most substances, alcohol breaks down at a nearly fixed pace regardless of how much is in your blood. Your body doesn’t clear it faster just because there’s more of it. This is why stacking drinks quickly raises your BAC while your liver plugs along at the same steady rate.
To put this in practical terms: if you have four drinks over two hours and then stop, you’ve consumed roughly four hours’ worth of processing while your liver has only worked through about two hours’ worth. You’re now carrying roughly two drinks’ worth of alcohol that still needs to be cleared, meaning you won’t hit zero for another two or more hours after your last sip. The math is simple, but people routinely underestimate it because they feel “fine” long before the alcohol is actually gone.
How Your Liver Breaks Down Alcohol
Your liver does the heavy lifting, handling over 90% of the work. The process happens in two main steps. First, an enzyme converts alcohol into acetaldehyde, a toxic compound and known carcinogen. Acetaldehyde is the molecule behind many of the worst hangover symptoms. Fortunately, a second enzyme quickly converts acetaldehyde into acetate, a much less harmful substance that eventually becomes water and carbon dioxide your body easily gets rid of.
In heavy, long-term drinkers, the liver activates a backup system to help with the extra load. This secondary pathway relies on a different enzyme that roughly doubles in activity in heavy drinkers compared to non-drinkers. That means chronic heavy drinkers may metabolize alcohol somewhat faster than occasional drinkers, but this comes at a cost: the backup pathway generates more harmful byproducts and contributes to liver damage over time.
Detection Windows by Test Type
How long alcohol is detectable depends entirely on what’s being tested. Here’s what to expect for each method:
- Breath test (breathalyzer): Detects alcohol for up to 12 to 24 hours after drinking, depending on how much you consumed.
- Blood test: Works for up to 12 hours after your last drink.
- Standard urine test: Picks up alcohol for roughly 12 to 24 hours.
- EtG urine test: This more sensitive test looks for a specific byproduct of alcohol metabolism rather than alcohol itself. After a few drinks, it can flag positive for up to 48 hours. Heavier drinking can push that window to 72 hours or longer.
- Hair follicle test: Detects patterns of alcohol use for one to six months. It takes several weeks after drinking for alcohol markers to show up in hair, so it’s not useful for detecting recent use. It’s designed to reveal repeated drinking over time.
The blood and breath windows track closely with actual impairment. The EtG and hair tests are different: they’re looking for metabolic traces, not active alcohol, and are typically used in legal, employment, or treatment monitoring settings.
Why It’s Faster or Slower for Different People
The one-drink-per-hour estimate is an average. Your actual clearance rate can vary meaningfully based on several factors.
Body Size and Composition
Alcohol is water-soluble, so it distributes through your body’s water content. People with more body water (generally those who are larger and have more muscle mass) dilute alcohol more effectively, resulting in a lower BAC from the same number of drinks. Men, on average, have more muscle mass and body water than women, which is one reason women typically reach higher blood alcohol levels from the same amount of alcohol and take longer to clear it.
Body mass index also plays a role in clearance speed. Research on breastfeeding women found that those with a higher BMI cleared alcohol from both their blood and breast milk significantly faster than women with a lower BMI. Women with a BMI over 25 reached zero alcohol in breast milk in about 5.2 hours on average, compared to 7.3 hours for women with a lower BMI. The relationship was roughly linear: more body mass, faster clearance.
Food in Your Stomach
About 20% of alcohol is absorbed directly through the stomach lining. The rest moves to the small intestine, where absorption is much faster. Eating before or while drinking slows the emptying of your stomach, which delays how quickly alcohol reaches your small intestine and enters your bloodstream. On an empty stomach, alcohol passes straight through and hits your blood rapidly, producing a higher, faster BAC spike. Food doesn’t change how fast your liver works, but it smooths out the curve by slowing absorption, which effectively makes the whole process feel more gradual.
Genetics
A genetic variant affecting the second step of alcohol metabolism is carried by roughly 30% of people with East Asian ancestry. People with this variant have reduced ability to break down acetaldehyde, the toxic intermediate. The result is slower overall alcohol metabolism, higher blood alcohol concentrations after the same amount of drinking, and unpleasant side effects like facial flushing and nausea. This variant is relatively rare in European populations, but when present in any group, it slows clearance and intensifies the body’s reaction to alcohol.
What Doesn’t Speed Things Up
Coffee, cold showers, exercise, and drinking water do not make your liver work faster. These might make you feel more alert, but your BAC drops at the same rate regardless. Hydration helps with hangover symptoms, and food slows absorption if you eat before or during drinking, but once alcohol is in your blood, only time and your liver’s fixed processing rate will clear it.
This is worth emphasizing because people often use “feeling sober” as a proxy for “being sober.” You can feel relatively normal while still carrying a BAC above the legal limit, especially if you’re used to drinking. The subjective feeling of sobriety returns before the alcohol is actually gone.
Practical Timelines
For a rough estimate of when you’ll be at zero BAC, count the number of standard drinks you’ve had, subtract the hours that have passed since you started drinking (your liver was working the whole time), and figure about one additional hour per remaining drink. A person who has five drinks between 8 p.m. and midnight has consumed five drinks over four hours. By midnight, their liver has processed about four drinks’ worth, leaving roughly one more hour before they’d reach zero, so around 1 a.m. at the earliest.
This is a simplification. Individual variation means you could be slower or faster by 20 to 30 percent. If you’re smaller, female, drinking on an empty stomach, or carry certain genetic variants, lean toward the slower end. If you’re larger with more muscle mass and you’ve eaten a full meal, you may clear alcohol on the faster side of the range. But the core math holds: your liver processes about one drink per hour, and nothing you do can rush it.