Do not drive after drinking. Not tonight, not tomorrow morning, not at any number this page shows you. This tool cannot tell you whether you are fit to drive, and neither can any calculator, app, watch or breathalyser you own. The only reliable way to be certain is to not drink and drive at all.
This page makes no accuracy claim whatsoever. It is a teaching illustration built on a population-average formula. Real people differ from it by margins large enough to make any individual number meaningless — food, medication, illness, liver function, genetics, sleep, hydration, how accurately you remember what you drank, and what the drink actually contained all move the answer, and none of them are in here.
No level shown here is described as safe, and none is. Impairment of judgement, reaction time and vision begins below every legal limit in the world, and legal limits are not safety thresholds — they are the point at which a particular jurisdiction decided to prosecute. The limits listed further down are shown as information about the law, not as targets, and never as permission.
If you have been drinking: get a taxi, take public transport, walk, or stay where you are. If you are worried about your drinking, speak to a doctor.
The shaded band is the same evening across the published population ranges; the line is the middle of it. Dashed lines are legal limits, shown as information about the law.
| Where | mg/100 mL | Also written | Note |
|---|
Alcohol spreads through the water in the body, so concentration is the dose ÷ that volume. The liver then removes it at a roughly constant rate per hour, whatever is left.
Drinks arrive through the stomach, not instantly, so each one passes through a first-order absorption step before it reaches the blood. That is the whole physiology in it.
The shaded region is the same drinks with the two shakiest inputs moved across their published ranges: distribution factor ±15%, elimination 0.010 to 0.025 g/100 mL per hour. Individuals fall outside it. Read the band, not the line.
Legal limits are not safety limits: impairment starts below every limit, and fatal-collision risk is raised well under 50 mg/100 mL. Do not drink and drive.
Alcohol leaves at a fixed rate per hour, and sleep does not change it. A heavy night finishing at 2 am can still be clearing at nine, which is when people drive to work believing the night is over.
Coffee, cold air, a shower, food afterwards, exercise: none changes the rate the liver works at. Some make you feel more alert while you remain exactly as impaired, and a person who feels fine is more dangerous than one who knows they are drunk.
A “glass of wine” runs from 125 to 250 mL and 11% to 15%, and a topped-up glass is uncountable. Even a perfect model fed a remembered evening gives a wrong answer, and the memory is usually the largest error in it.
No. Nothing on this page describes any level as safe, because none is. Impairment begins below every legal limit that exists. This is a population-average illustration with uncertainty far larger than the differences people try to use it to decide between, and it knows nothing about you beyond the numbers you typed. Do not drive after drinking.
No, and it deliberately does not try. It will not print a time, because that number would be wrong for a large share of people who read it, and because being under a legal threshold is not the same as being fit to drive. The morning after a heavy night is the case people misjudge most often — alcohol is still being cleared long after the drinking stopped, and sleep does not speed that up.
Because the published range across healthy adults really is that wide: roughly 0.010 to 0.025 grams per 100 mL per hour, a factor of two and a half. You cannot know your own figure without a blood test series, so the honest reading of the slider is that it shows how little the model can pin down, not that you should pick your favourite value.
No. None of them changes how fast the liver clears alcohol. They can make somebody feel more alert while remaining just as impaired, which is worse than feeling drunk. Food eaten before drinking slows absorption and lowers the peak; it does not reduce the total.
Because the published equations for how alcohol distributes were derived separately, from groups with different average body composition — the relevant variable is body water, not identity. Neither formula describes any particular person. If you sit away from the average your formula assumes, it will be wrong about you, which is one more reason to read the band rather than the line.
Releases in which this page changed, newest last. Derived from the archived copy of every release, not from notes written afterwards — so it reflects what actually shipped. Site-wide passes are left out; they are in the full changelog.