Your body metabolizes alcohol at a fairly constant rate of about 0.015% blood alcohol concentration (BAC) per hour. In practical terms, that works out to roughly one standard drink per hour. This rate is remarkably steady regardless of how much you’ve had, because the primary enzyme responsible for breaking down alcohol works at a fixed capacity.
The Standard Rate and What It Means
The average person’s liver clears alcohol at about 0.015 grams per 100 milliliters of blood per hour. That number is the central estimate used in both clinical and forensic settings, though the actual range across individuals falls between 0.010% and 0.020% per hour. If your BAC is 0.08% (the legal driving limit in most U.S. states), it would take roughly five to six hours for your body to fully eliminate the alcohol, not two or three as many people assume.
One standard drink contains about 14 grams of pure alcohol. That’s 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of distilled spirits. Since the liver can process approximately that amount in an hour, the “one drink per hour” guideline holds up well as a rough estimate. But it’s only rough. Stronger drinks, larger pours, and individual biology all shift the math.
How Your Liver Breaks Down Alcohol
Alcohol metabolism happens in two main steps inside the liver. First, an enzyme called alcohol dehydrogenase (ADH) converts the alcohol into acetaldehyde, a toxic compound and known carcinogen. Acetaldehyde is what causes much of the damage associated with heavy drinking, but it’s normally short-lived. A second enzyme, aldehyde dehydrogenase (ALDH), quickly converts acetaldehyde into acetate, which the body then breaks down into water and carbon dioxide for easy elimination.
A backup system kicks in when you drink heavily. A separate enzyme pathway in the liver becomes active only after large amounts of alcohol have been consumed, helping process the excess. Under normal drinking conditions, though, ADH and ALDH do almost all the work, and they operate at a fixed speed. That’s why drinking coffee, eating food after the fact, or taking a cold shower does nothing to speed up the process. Time is the only thing that removes alcohol from your system.
Why Women Metabolize Alcohol More Slowly
Men and women process alcohol differently, and the gap is larger than most people realize. Men have active ADH enzymes in both their stomach lining and their liver, while women have almost no ADH in their stomach at all. The presence of this stomach enzyme in men can reduce alcohol absorption by as much as 30% before it even reaches the bloodstream. Women also tend to have less active forms of the liver enzyme.
Body composition compounds the difference. Women typically carry a higher percentage of body fat and a lower volume of total body water compared to men of similar weight. Since alcohol dissolves in water, less body water means the same number of drinks produces a higher concentration of alcohol in the blood. These two factors together explain why a woman and a man who weigh the same and drink the same amount will often have meaningfully different BAC levels.
How Age Changes the Equation
Alcohol hits harder as you get older, and the reason is physiological. Total body water decreases with age, which raises blood alcohol concentration after the same number of drinks. The liver also processes alcohol more slowly in older adults, meaning elimination takes longer. According to Harvard Health, older people end up with higher BAC levels than younger people after drinking identical amounts, a combination of reduced body water and slower clearance rates. Medications common in older adults can further interfere with metabolism, compounding the effect.
Genetics and the “Flush” Response
A genetic variant affecting the ALDH enzyme is carried by roughly 30% of people with East Asian ancestry. This variant produces an enzyme with low activity, meaning acetaldehyde builds up in the body instead of being efficiently cleared. The result is the well-known “Asian flush” reaction: facial redness, nausea, and rapid heartbeat after even small amounts of alcohol.
Beyond the uncomfortable symptoms, this genetic difference also slows the overall rate of alcohol metabolism. Research has shown that pharmacologically inhibiting ALDH activity (mimicking the genetic variant) produces about a 10% decrease in the speed of alcohol clearance. People with this variant aren’t just experiencing unpleasant side effects; their bodies are genuinely processing alcohol at a reduced pace, which means alcohol and its toxic byproduct stay in their system longer.
Factors That Don’t Speed Things Up
Because alcohol metabolism is enzyme-limited and essentially linear, very few things can meaningfully accelerate it. Eating before or while drinking slows absorption into the bloodstream, which keeps your peak BAC lower, but it doesn’t change how fast your liver clears what’s already there. Exercise, hydration, and sleep don’t increase the enzymatic rate either. They may help you feel better, but your BAC drops at the same 0.015% per hour regardless.
The only factor that modestly increases elimination rate is chronic heavy drinking, which upregulates that backup enzyme pathway in the liver. This is not a benefit. It reflects liver adaptation to a toxic load and comes with increased production of harmful byproducts that damage liver cells over time. Tolerance to alcohol’s effects is not the same as safe or efficient processing of it.
Estimating Your Own Timeline
To estimate how long alcohol will stay in your system, start with your approximate BAC and divide by 0.015. If you’ve had three standard drinks in an hour on an empty stomach, a 160-pound man might reach a BAC around 0.06%. From the point you stop drinking, it would take about four hours to reach zero. A lighter person, a woman, or someone older would start from a higher BAC and take proportionally longer.
Keep in mind that “standard drinks” are smaller than what most people pour. A generous glass of wine is often 7 or 8 ounces rather than the 5-ounce standard, and a strong cocktail can contain two or three shots. If you’re doing the math, count the actual alcohol content rather than the number of glasses. The liver doesn’t care how the drink was served. It processes about 14 grams of pure alcohol per hour, and everything beyond that waits in line.