Hangover Calculator
How long this one is likely to last, and what your body is actually doing while you wait. Ranges, from the published research — no cures for sale.
The band starts from published research: sampled every two hours in 811 drinkers, hangovers averaged 18.4 hours from the last drink, with most falling between 14 and 23. Your inputs move it from there. It is a range because the evidence is a range.
Hour nought is your last drink. Most people are asleep for the first stretch of this, which is why the worst of it lands after waking.
Every number on this page is a range because every source behind it is a range, and none of them measured you. Time is the only thing that ends a hangover; everything below makes the wait easier rather than shorter.
Last night
Count in standard drinks: a 12 oz beer, a 5 oz glass of wine or a single shot is one each. A large pour or a strong beer is more.
And after
Sleep is the one input the duration research ties directly to the clock — and it does not move it in the direction most people expect.
What moved this estimate
Every input, what it did to the range, and why. Nothing here is hidden in a black box.
| Effect | What | Why |
|---|---|---|
| +2 h | 6 drinks in 4 hours | That is 2 standard drinks past the roughly one-an-hour pace your liver keeps up with, so the alcohol was still clearing after you stopped. The hangover clock only starts when the alcohol is nearly gone, so the whole window slides later. |
| 0 h | 6 hours of sleep | Five to seven hours sits at the middle of the anchor study, where the average was 18.3 hours. Sleep is the input the research ties most directly to duration. |
| Severity | Six or more drinks | Enough to put you in hangover territory for most people. Dose shows up in severity more than in the clock. |
| No change | Your age band | Through the thirties the physiology has barely moved. What usually changes is what a lost day costs — the hangover is the same size and the room it has to fit into is smaller. Age changes the copy here, not the clock — there is no published age adjustment to the duration figure worth pretending to. |
Hour by hour, from your last drink
A hangover develops as blood alcohol concentration approaches zero, which is why the worst of it arrives after the drinking is long over.
Still clearing
Blood alcohol is falling but not gone. Symptoms are mild or absent and sleep is shallow and broken — alcohol front-loads deep sleep and takes REM away in the second half of the night. You may still be over a driving limit; the alcohol system calculator puts a range on that.
The turn — and the peak
The hangover develops as blood alcohol approaches zero, so this is where it announces itself. Alcohol had been lifting calming GABA signalling and damping glutamate; the swing back the other way is jitter, dread, and light and noise that are suddenly too much. This is hangxiety’s window.
Inflammation and a sleep debt
Headache, nausea, thirst, and a body that feels like it fought something. An inflammatory response and disrupted mitochondrial function are on the short list of mechanisms; the sleep you had was not the sleep you needed, and that shows up here as fog rather than pain.
The long middle
Nothing dramatic, nothing improving quickly. This is the stretch water, food and a dark room are for. Concentration comes back before mood does.
The tail
Symptoms fade unevenly and appetite returns first. Most people are done by the far end of this window. If you are not — if the second day brings shakes or sweats — that is the paragraph about withdrawal, further up this page.
What actually helps
All of it makes the wait easier. None of it makes the wait shorter.
- Time. The only thing that ends a hangover. Everything below is comfort while it runs.
- Water and food. Fluid loss and low blood sugar are real parts of the picture, and both are easy to fix. Fixing them treats symptoms, not the process.
- More sleep, if you can get it. Short sleep tracks with rougher hangovers — in one study of 578 drinkers, total sleep time correlated negatively with hangover severity.
- Painkillers, carefully. They treat the headache. Paracetamol goes through a liver that has had a long night, and anti-inflammatories are hard on a stomach alcohol has already irritated — read the label, and never double up.
- A quiet room. Light and noise sensitivity are part of the syndrome. Lowering the input is free and it works.
What does not
A 2022 systematic review of randomised placebo-controlled trials found only very low quality evidence for any pharmacologically active hangover treatment.
- Hair of the dog. A hangover develops as blood alcohol approaches zero, so another drink pushes that moment later. It is a postponement with more alcohol attached, and NIAAA lists a drink the next morning among the things that will not cure a hangover. Needing one to steady up is a different signal — see below.
- Coffee. Changes how awake you feel. Changes nothing about how fast alcohol or its metabolites leave.
- Sweating it out. The liver does essentially all of the work at its own pace. A run adds dehydration to a body that is short of fluid.
- Supplements, sachets and drips. That is the aisle the systematic review above was reviewing when it found very low quality evidence.
- A greasy breakfast. Food matters before drinking, where it slows absorption and lowers your peak. Afterwards it is breakfast — welcome, but not a treatment.
If the worst part is the dread
The morning anxiety has a name and a mechanism. Alcohol lifts calming GABA signalling and damps glutamate while you drink; as it clears, the brain swings the other way, and the swing arrives as jitter, dread and a replay of everything you said. Reviewing the biology, Palmer and colleagues concluded that alcohol metabolites, neurotransmitter alterations, inflammatory factors and mitochondrial dysfunction are the most likely factors in hangover pathology — with particular reference to glutamate. Broken sleep and low blood sugar sharpen it. It passes as the chemistry resettles. Our full piece on hangxiety covers why it lands hardest on people who were already anxious.
When it is not a hangover.
Hangover and early withdrawal overlap in the morning and then part ways. A hangover eases through the day and does not care whether you drink. Withdrawal sharpens, and it settles when alcohol goes back in. Shaking hands, sweating, a racing pulse, or a morning drink that fixes all three — that pattern belongs to a different page. In physically dependent drinkers, alcohol-related seizures typically occur 8 to 48 hours after the last drink, which is exactly the window a “two-day hangover” occupies. The withdrawal risk checker takes two minutes and tells you which conversation you are having.
This is data for next time, not a verdict on last night.
A rough morning is information: about pace, about the finish time, about how much of it was the last two rounds. Most people who run this twice — once after a heavy night, once after a lighter one — find a threshold that separates a fine morning from a lost day, and that threshold is more useful than a resolution. The one lever that reliably moves it is the night itself: alternating alcoholic and alcohol-free drinks one for one roughly halves the total without shortening the evening, and the units calculator shows how fast a large glass of wine stops counting as one drink.