Can you still be over the limit the next morning?

The liver works at a fixed pace

Most things your body gets rid of leave faster when there is more of them. Alcohol does not. Once it is in your blood, the liver breaks it down at a nearly constant rate — roughly 0.15 ‰ per hour for an average adult, or 0.015 % in US units. Ten times as much alcohol takes ten times as long.

That makes the arithmetic of the morning after very simple and very unforgiving. The time you need is your peak divided by the hourly rate. Nothing that happens overnight changes the rate: not sleep, not water, not coffee at seven, not a cold shower, not a big breakfast. You wake up feeling better because you have slept, not because your blood is clear.

Hours from a given peak

The table below shows how long it takes from a peak to reach zero, and to fall below the 0.8 ‰ US limit. Find your likely peak in the BAC chart, or let the calculator work it out from your actual drinks.

Read the second column first. From 1.2 ‰, an evening most people would call a heavy night out, the liver needs eight hours to clear everything, and twelve if it is a slow one. From 2.0 ‰ it needs more than thirteen, or twenty on a slow liver. Those hours count from the moment alcohol was in the blood, not from when you went to bed.

Three ordinary evenings

After-work drinks

An 80 kg man has four 0.33 l bottles of 5 % beer between six and nine. On the average model he peaks around 0.96 ‰ and is at zero roughly 6:23–9:34 after the first bottle — around midnight or a little before. Driving home at nine would have been illegal in most of Europe and close to the limit in the United States. Driving to work the next day is fine on average. On a bad day, with a slower liver, it is the first two hours after midnight that remain uncertain.

A wedding

A 65 kg woman drinks a glass of sparkling wine at four, three glasses of wine with dinner and two more later: six drinks over eight hours. On the model she peaks well over 1 ‰ and needs about 15:53–23:50 from the first glass to reach zero. If the first glass was at four in the afternoon, that is the middle of the night — but only on the average curve. With a liver at the slower end of normal she is still above zero after breakfast.

A big night

A 70 kg man drinks six half-litres of 5 % beer between ten and two. He peaks near 2.49 ‰. At eight the next morning, ten hours after the first beer, the model puts him at about 0.99 ‰ — above the limit in Norway, Sweden and Poland, and close to it almost everywhere else. Sleeping in until eleven does not help much: he is still not at zero.

Why "I feel fine" is the wrong test

Tolerance is real, but it is a tolerance of feelings, not of chemistry. A regular drinker at 0.6 ‰ may feel completely normal and still react more slowly, judge distances worse and take more risks than they would sober. The law in most countries does not ask how you feel: in Germany, Norway, Finland, France, Sweden and Poland the offence is the number in your blood or breath, with no need for the police to show you were driving badly.

The morning adds its own problems. You are tired, you may be dehydrated, you have probably slept badly. All of those make a modest blood alcohol level more dangerous, not less. Research on hungover drivers finds impairment even when the reading has reached zero.

How to plan around it

1. If you need to drive in the morning, decide before the first drink how much you will have and when you will stop. Afterwards, that decision is made by someone with less judgement.
2. Work backwards: from your departure time, subtract the hours the calculator gives you, plus a generous margin. That is your last drink.
3. Use the elimination calculator with clock times so it tells you the hour you should be at zero, not just the number of hours.
4. If the answer is anywhere near your departure time, do not drive. Take a train, a taxi or a lift, or start later.
5. Remember that several countries set zero for new drivers. For them, any trace the next morning is already an offence — see the legal limits page.

A calculator can tell you when you are certainly not fit to drive. It can never tell you that you are. The only safe reading is 0.00.

What the police find

Morning checks are a routine part of drink-driving enforcement in many countries precisely because so many drivers are caught on the way to work. A breath test at seven measures exactly what is in your lungs at seven; it does not care that you stopped drinking at one or that you slept. Fines, licence points and bans follow the same rules as an evening offence.

The short version

Alcohol leaves your body at about 0.15 ‰ an hour, 0.10 if you are a slow eliminator, and nothing makes it go faster. A night that ends above 1 ‰ needs most of the following morning to clear. Plan your drinking around your driving, not the other way round, and when in doubt, leave the car.