Your body clears alcohol at a remarkably steady rate: about one standard drink per hour. If you had four drinks, you’re looking at roughly four to five hours before your blood alcohol level drops back to zero. That rate barely budges no matter what you do, because the liver can only process so much at a time.
But “out of your system” means different things depending on why you’re asking. If you’re wondering when you’ll be sober enough to drive, the math is straightforward. If you’re worried about a drug test, the answer depends entirely on the type of test.
How Your Liver Processes Alcohol
Nearly all the alcohol you drink is broken down in the liver through a two-step process. First, an enzyme converts alcohol into a toxic byproduct called acetaldehyde (a known carcinogen). A second enzyme then converts acetaldehyde into acetate, which the body easily breaks down into water and carbon dioxide.
The key detail is that these enzymes max out quickly. Even after just one or two drinks, they’re essentially working at full capacity. This means your liver processes alcohol at a fixed rate regardless of how much is in your bloodstream. Drink more, and the excess just waits in line. The average person lowers their blood alcohol concentration (BAC) by about 0.015 to 0.020 per hour. At the legal limit of 0.08, that translates to roughly four to five hours to reach zero.
People who drink heavily over long periods do develop a secondary breakdown pathway that kicks in at higher concentrations, but this doesn’t meaningfully speed up the process for most people.
What Counts as One Drink
When people say “one drink per hour,” they mean one standard drink, which contains about 14 grams of pure alcohol. In practical terms, that’s:
- Beer: 12 ounces of regular-strength beer (about 5% alcohol)
- Wine: 5 ounces of wine (about 12% alcohol)
- Spirits: 1.25 ounces of 80-proof liquor
This is where people miscalculate. A strong IPA at 8% alcohol in a pint glass is closer to two standard drinks. A generous pour of wine at a restaurant can easily be seven or eight ounces, not five. If you’re trying to estimate when you’ll be at zero, count your actual alcohol intake, not just the number of glasses.
Factors That Change Your Timeline
The one-drink-per-hour rule is an average, and individual variation is real. Your genetics play the biggest role. The enzymes responsible for breaking down alcohol come in different versions depending on your ancestry, and some variants work significantly faster or slower than others. This is why some people of East Asian descent experience intense flushing and nausea after small amounts of alcohol: they have a less efficient version of the second enzyme, causing toxic acetaldehyde to build up.
Body size and composition matter too. A smaller person reaches a higher BAC from the same amount of alcohol, so even though they may clear it at a similar hourly rate, they’re starting from a higher peak and will take longer to get to zero. Women generally reach higher BAC levels than men from the same number of drinks, partly due to differences in body water content and enzyme activity.
Food Makes a Bigger Difference Than You Think
Eating before or while you drink is one of the few things that genuinely changes how alcohol moves through your body. Food in your stomach slows the rate at which alcohol enters your bloodstream, which lowers your peak BAC and spreads absorption over a longer window. This is the main reason you feel less drunk when you drink with a meal.
But food does something else that’s less well known: it temporarily speeds up the liver’s processing rate. Research published in the Annals of Emergency Medicine found that a high-carbohydrate meal increased the alcohol elimination rate by 86% in the two hours after eating, compared to fasting. That boost faded by four hours, returning to the baseline rate. So eating doesn’t just delay absorption; it briefly helps your liver work faster too.
Coffee, Cold Showers, and Other Myths
Nothing you do will force your liver to work faster in a meaningful way. Coffee makes you feel more alert, but it doesn’t lower your BAC. Cold showers, exercise, fresh air, and drinking water are all irrelevant to the rate of alcohol elimination. They may change how you feel, but your liver is still clearing alcohol at the same fixed pace. Time is the only thing that actually works.
This matters most in the morning after heavy drinking. If you had six drinks ending at midnight, your BAC may not reach zero until 5 or 6 a.m., and that assumes you stopped at midnight. People routinely drive the morning after a night out while still technically impaired.
How Long Alcohol Shows Up on Different Tests
If your concern is a test rather than sobriety, the detection window depends on what’s being measured.
Breath and blood tests detect alcohol itself, not its byproducts. These are positive only while alcohol is actively in your bloodstream, so the window is roughly the same as the time it takes your BAC to hit zero. For most people, that’s a matter of hours after the last drink.
Standard urine tests for alcohol also have a short window, generally similar to blood tests. However, a specialized urine test looks for a metabolite called EtG (ethyl glucuronide), which your body produces as it breaks down alcohol and which lingers much longer. Commercial EtG tests are marketed as detecting drinking up to 80 hours after the fact. In practice, their reliability drops significantly beyond 24 hours. One study found that while EtG tests were reasonably accurate at detecting drinking within the past day (about 74% sensitivity), their ability to detect any drinking within the past three days was poor, catching fewer than half of cases. So the “80-hour” claim on the box overstates what the test reliably delivers.
Hair follicle tests operate on a completely different timeline. Alcohol metabolites get deposited in hair as it grows, and a standard hair test covers about 90 days of growth. In some cases, alcohol can be detected in hair for up to six months. These tests are used to establish patterns of heavy drinking over time, not a single episode.
A Quick Estimate for Your Situation
To roughly calculate when your BAC will reach zero, count your standard drinks (being honest about pour sizes), then assume about one hour of processing per drink, starting from when you had your last one. If you had five standard drinks and your last sip was at 11 p.m., expect to be at or near zero sometime around 4 a.m., possibly later if you’re smaller, female, or drank on an empty stomach.
This is an estimate, not a guarantee. Individual metabolism varies enough that two people drinking the same amount can have meaningfully different timelines. If the stakes are high, whether that’s driving, a test, or a medical situation, build in extra time.