How Long Does Alcohol Stay in Your System?

Two different questions, two different answers. Build your night below for an estimate of when the alcohol leaves your blood — then see how long each kind of test can still find evidence of it.

What did you drink?

Your drinks

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Name

Size

ABV %

A US standard drink is 14 grams of pure alcohol — NIAAA's definition. Anything you add here is converted to that unit.

You, and the clock

Hours since your last drink 0 hours

0 h 24 h

Body weight

Biological sex

This sets the Widmark distribution factor — about 0.68 for men and 0.55 for women, because alcohol spreads through body water and the average share of body water differs. It is a population average, not a reading of you.

Estimated time until the alcohol is gone

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Standard drinks

0 g

Pure alcohol

0.00

Estimated peak BAC

No calculator can clear you to drive

This is arithmetic on population averages. It cannot measure your impairment, your liver, your medication or the food you had, and it is not a defence at a roadside stop. Impairment starts well below every legal limit. If you have been drinking, the honest plan is another way home — the drink driving limit page covers what the law actually says, and the BAC calculator covers the drinking window itself.

What this estimate assumes

Every drink is counted as already in your blood when the clock starts. Spread across an evening your real peak was lower, so a long slow session finishes sooner than this shows.
Your liver clears alcohol at a fixed pace you cannot speed up. The published physiological range is 10 to 35 mg per 100 mL of blood per hour; the range above runs from 20 down to 10, which covers most people who are not drinking heavily every day. Regular heavy drinkers clear faster, at 25 to 35.
A US standard drink is 14 grams of pure alcohol. The NHS puts what an average adult processes in an hour at 8 grams — so "one drink an hour" is a floor, not a promise, and a 14 gram drink is closer to an hour and three quarters.
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How long a test can still find it

Clearance and detection are different questions. Breath, blood and saliva tests look for ethanol itself, so they follow the clock above. Urine and hair tests look for what your liver left behind, and those markers outlast the alcohol by days or months. Every window here is a range, because that is how the research reports it — and a laboratory's cut-off moves the answer as much as your drinking does.

Test	What it looks for	How long it can find it
BreathEthanol	Ethanol crossing from blood into lung air	Tracks your blood level in near real time, so it goes negative on the same clock as the estimate above — hours, not days.
BloodEthanol	Ethanol in the blood itself	10 to 12 hours after the last drink in the biomarker review literature, depending on how much was in you to start with.
SalivaEthanol	Ethanol in oral fluid	Saliva profiles agree closely with blood and breath, so roughly the blood window — a few hours after a light night, most of a night after a heavy one.
UrineBoth	Ethanol on a plain test; EtG and EtS on a metabolite test	Plain ethanol test: like blood, 10 to 12 hours after the last drink. EtG / EtS metabolite test: detectable within the hour, about 24 hours after small quantities and up to 130 hours after heavy consumption. Followed through detox, heavy drinkers took a median of roughly 78 hours to fall below the cut-off, spread from about 40 to 130.
HairMetabolite	EtG laid down in the hair shaft as it grows	Several months, read from a 3 to 6 cm segment. This one is not about a night at all — it reads a pattern of drinking over a season.

The "80-hour EtG test" is a marketing label

The peer-reviewed window is wider and less tidy than the round number sold with the test: about 24 hours after small quantities, up to 130 after heavy consumption. The same review records positives from ethanol-containing mouth rinses and hand sanitiser, and notes that 2.5 litres of alcohol-free beer can produce a positive EtG result for up to 20 hours. If a test is what brought you here, the useful questions are which test, which cut-off, and what window the laboratory itself claims.

These windows describe the tests, not you. They come from published studies of groups of people, and individual results vary by more than any calculator can narrow down. Our full evidence page, how long alcohol stays in your system, works through each one with the sources in line.

How this is calculated

Clearance is estimated with the Widmark equation — body weight, biological sex, grams of pure alcohol consumed and time elapsed — using a body-water distribution factor of roughly 0.68 for men and 0.55 for women, a US standard drink of 14 g of pure alcohol, and an average elimination rate of about 0.015% BAC per hour, which works out near one standard drink an hour. Detection windows are separate from clearance and come from the testing literature rather than from your inputs: breath and blood follow the alcohol itself and clear first, urine EtG follows a metabolite and lasts far longer, and hair testing reflects months of pattern rather than one night. Every figure on this page is a range because the research is a range: elimination rates differ between people by a factor of two or more, and detection times shift with the laboratory cut-off, the amount drunk and the drinking history. In one study of heavy drinkers followed through detoxification, urinary EtG took a median of about 78 hours to fall below the cut-off, with individual times spread from roughly 40 to 130 hours. Nothing here is a measurement of you.

Sources

Our editorial policy explains how these tools and articles are researched and kept up to date.

Why this matters

Most people searching this are asking one of two very different questions, and getting the wrong answer to the one they meant. The first is about clearance: when is the alcohol actually out of me? The second is about detection: when will a test stop finding evidence that I drank? Those two answers are separated by a factor of a hundred, because most modern alcohol testing does not look for alcohol at all. It looks for what your liver left behind.

The clearance side is the one where a single confident number does real damage. Elimination is steady and slow: NIAAA describes the body metabolising alcohol at a rate that does not change with how much you drank or with attempts to sober up on caffeine. What that rate is, exactly, is a range rather than a constant — a review of the forensic literature puts the physiological spread at 10 to 35 mg per 100 mL of blood per hour, with about 15 typical for moderate drinkers who have eaten and 25 to 35 in people drinking heavily every day. A tool that reports one hour from that spread is not more accurate. It is just quieter about being wrong.

The familiar rule — one standard drink an hour — is a floor rather than a promise, and the two official definitions show why. A US standard drink is 14 grams of pure alcohol. The NHS, building the same physiology into the UK unit system, puts one unit at 10 ml or 8 grams, around what an average adult processes in an hour. Eight grams an hour against a fourteen-gram drink is most of two hours, not sixty minutes. That gap is exactly why people wake up still over a limit after a night they thought they had slept through.

The detection side runs on different chemistry, and the number people quote each other is usually a product label rather than a finding. EtG in urine is detectable about 24 hours after small quantities and up to 130 hours after heavy consumption — a spread wide enough that the same test means different things for a glass of wine and for a weekend. Hair testing reads months. Neither is a verdict on a person, and no page can tell you what a particular laboratory's cut-off will do.

None of this is a scoreboard. A late night is information about pace and quantity, and the arithmetic is the same for everyone regardless of how the evening went. If the pattern is what you want to change rather than the morning, alternating drinks one for one lowers the peak you have to clear at all.