Hangover Duration Calculator

A hangover starts as your blood alcohol gets back to about zero, and in the biggest study of how long it lasts, it was over on average 18.4 hours after the last drink.

For most drinkers that came out between 14 and 23 hours, or roughly 12 hours from waking up. The study is Lantman, Mackus and Verster (2018), with 811 Dutch students timing their own hangovers.

The surprise in that data is what did not matter. How long the hangover lasted did not track the number of drinks, or the estimated blood alcohol. Sleep did. People who slept over 7 hours had milder hangovers that ran slightly longer (19.2 hours on average), probably because they slept through more of the worst part. People on under 5 hours had the roughest ones, over a little sooner at 17.5.

So this page does two separate jobs. It works out when the alcohol itself is gone, which you can calculate for one person. Then it puts the survey’s hangover figures on top, which you cannot.

When the alcohol clears

This is the Widmark formula, the same one the Alcohol Metabolism Calculator uses, so the two pages agree.
BAC % = grams of alcohol / (body weight in grams × r) × 100
r = 0.68 for men and 0.55 for women, because women carry less body water per kilo
Elimination = 0.015% an hour, a steady rate that coffee, cold showers and a big breakfast do not change
A US standard drink is 14 g of alcohol: 12 oz (355 ml) of 5% beer, 5 oz (148 ml) of 12% wine, or 1.5 oz (44 ml) of 40% spirits.

Worked example: an 80 kg man has 6 drinks over 4 hours. That is 84 g of alcohol, and 84 / (80,000 × 0.68) × 100 = 0.154%. Take off 4 hours at 0.015% and his estimated peak is 0.094%.
The alcohol is gone 0.094 / 0.015 = about 6.3 hours after his last drink. The hangover is usually over about 18 hours after it.

Weight matters because the same alcohol spreads through more body water in a bigger body. A 200 lb (91 kg) man ends up with a lower blood alcohol than a 130 lb (59 kg) man on the same drinks. His liver is not working any faster.

Is a hangover likely? Researchers treat an estimated peak of 0.11% as enough to cause one (the Alcohol Hangover Research Group set it in 2010). About a quarter of drinkers who reach it report no hangover at all. A 2020 review by Verster and colleagues found plenty of hangovers below 0.11% too, so read the cutoff as a guide rather than a line.

Water helps less than you have been told. Alcohol does make you pee more, roughly 100 ml extra for every 10 g, by blocking vasopressin, the hormone that tells your kidneys to hold on to water. But hangover and dehydration turn out to run side by side rather than one causing the other. In Verster’s survey of 826 students, the ones who drank water felt only slightly better the next day, and a later review by the same group reached the same view. Drink the water anyway, because it slows the drinking down. Just do not expect it to cancel the drinks.

Do not drive on a hangover because the alcohol is gone. In Verster’s driving simulator studies, hungover drivers with zero blood alcohol drove about as badly as drivers at 0.05% to 0.08%.

Painkillers. Both common kinds carry an alcohol warning on the US label for anyone having 3 or more drinks a day: acetaminophen (Tylenol) for the liver, and ibuprofen, naproxen and aspirin for stomach bleeding.

Congeners are the other products of fermentation in a drink. Dark drinks such as bourbon, brandy and red wine carry more of them than vodka or gin, and in a 2010 trial by Rohsenow and colleagues, bourbon gave worse hangovers than vodka at the same blood alcohol.

What causes the hangover itself is still argued over. It begins as the alcohol leaves, so it is not simply being drunk, and acetaldehyde (the toxic first product of breaking alcohol down) is mostly cleared by then. The strongest leads are an immune response, since inflammatory markers run high in hungover drinkers, and badly broken sleep.

Time is still the only cure anyone has found.