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Hangover Calculator

Predict tomorrow morning before it happens. Enter what you drank and get a personalized hangover risk score.

About You

What Did You Drink?

Conditions

Hangover Risk Score
1.4
Mild
Est. peak BAC: 0.023%  · Recovery: ~4h

Expected Symptoms

  • • Mild headache

Tips to Reduce Your Hangover

  • → Try to match every alcoholic drink with a glass of water next time.

Disclaimer:This calculator provides rough estimates only based on average metabolism rates. It should NOT be used to determine whether you are fit to drive or operate machinery. Individual BAC varies based on metabolism, medications, health conditions, food intake, and many other factors. The only reliable way to measure BAC is with a calibrated breathalyzer or blood test. Never drink and drive. If you need help with alcohol, call SAMHSA: 1-800-662-4357.

How the Hangover Risk Score Works

The calculator weights six factors that clinical research has linked to hangover severity. Alcohol load carries the most weight — peak BAC drives about 35% of the score — because total ethanol exposure is the single strongest predictor of how bad you will feel. Drinking speed accounts for another 20%, since rapid consumption overwhelms your liver's ability to process acetaldehyde at a steady rate.

Congener content from your drink choices contributes 15%. Bourbon contains roughly 37 times more congeners than vodka, which is why the same number of bourbon drinks produces a measurably worse morning — we break down the full science in our hangover cures guide. Hydration, food, and sleep split the remaining 30% equally, each modifying the baseline that alcohol and congeners establish.

Congeners: Why Your Drink Choice Matters

Congeners are chemical byproducts of fermentation and aging. They give whiskey its color, red wine its complexity, and your morning its misery. The darkest spirits — bourbon, scotch, brandy — sit at the top of the congener scale. Clear spirits like vodka and gin sit near the bottom.

This is not folk wisdom. Researchers at Brown University gave subjects enough bourbon or vodka to reach identical BAC levels, then measured hangover severity the next morning. Bourbon drinkers scored worse on every symptom metric despite having the same blood alcohol peak. The extra congeners — particularly methanol, which your body converts to formaldehyde — added a chemical insult on top of the ethanol itself.

Red wine falls in the middle of the congener spectrum but adds another compound: tyramine, which can trigger headaches independently. White wine and champagne contain fewer congeners than red, making them a marginally better choice if hangover avoidance is the goal.

Dehydration Is Half the Battle

Alcohol suppresses vasopressin, the hormone that tells your kidneys to retain water. Alcohol suppresses the hormone that tells your kidneys to retain water, so each drink flushes out more fluid than you took in. Four drinks over three hours — roughly four standard drinks — can leave you significantly dehydrated — enough to cause headache, fatigue, and difficulty concentrating the next day even without other hangover mechanisms.

Matching each drink with a glass of water replaces most of that lost fluid in real time. It will not touch the acetaldehyde buildup or the inflammatory response, but it eliminates the dehydration layer entirely. That alone can drop a moderate hangover to a mild one.

Food and Absorption Speed

A full stomach slows alcohol absorption significantly — research shows reductions in peak BAC ranging from 25% for a small snack to over 60% for a full meal — which means your liver gets more time to process each wave of ethanol before the next one arrives. The effect is strongest with meals high in fat and protein — a burger before going out does more than a salad. Eating after drinking helps less, since absorption is already underway.

Sleep and Recovery

Alcohol disrupts REM sleep, the phase your brain needs for cognitive restoration. Even if you sleep eight hours after heavy drinking, the quality of that sleep is substantially worse than sober sleep. Getting fewer than six hours compounds the problem — your body is simultaneously processing a toxin and running on a sleep deficit.

The calculator penalizes low sleep because every clinical measure of hangover severity correlates with sleep duration. Less sleep consistently correlates with worse hangover symptoms in clinical observations, though the exact multiplier varies by individual.

What This Calculator Cannot Measure

Individual genetics, liver enzyme levels, medication interactions, chronic health conditions, and tolerance built from regular drinking all influence hangover severity in ways no calculator can capture. The score is an estimate based on population averages, not a personalized medical assessment. If you consistently experience severe hangovers from moderate drinking, that pattern is worth discussing with a doctor. For a more precise BAC estimate, use our BAC calculator, and check the sober calculator to see when you will be back to 0.00%.

Frequently Asked Questions

What causes a hangover?
Hangovers result from several overlapping mechanisms. Alcohol is a diuretic that depletes fluids and electrolytes. Your liver converts ethanol into acetaldehyde — a toxic compound that triggers nausea and headaches — before breaking it down further. Alcohol also disrupts sleep architecture, irritates the stomach lining, and triggers an inflammatory immune response. The combined effect is what you feel the morning after.
Do darker drinks really cause worse hangovers?
Yes. Darker spirits like bourbon, whiskey, and red wine contain higher levels of congeners — byproducts of fermentation that include methanol, acetone, and tannins. A controlled study published in Alcoholism: Clinical and Experimental Research found that bourbon drinkers reported significantly worse hangovers than vodka drinkers at the same BAC level. The calculator factors in congener content for each drink type.
Does drinking water between drinks actually help?
It helps with dehydration symptoms — headache, dry mouth, dizziness — but it does not speed up alcohol metabolism or prevent all hangover effects. Matching each alcoholic drink with a glass of water reduces the dehydration component, which is why the calculator lowers your risk score when hydration is higher. It will not eliminate a hangover from heavy drinking, though.
Can you prevent a hangover completely?
The only guaranteed prevention is drinking less or not at all. Beyond that, eating a full meal before drinking, staying hydrated, choosing low-congener drinks like vodka or white wine, pacing yourself to one drink per hour, and getting a full night of sleep all reduce severity. None of these eliminates hangover risk entirely once you pass about four standard drinks.
How long does a hangover last?
A mild hangover (score 1-3) typically clears within 4-6 hours. Moderate hangovers (score 3-5) can last 8-12 hours. Severe hangovers (score 6-8) may persist for 14-20 hours, and a brutal hangover from very heavy drinking can take over 24 hours to fully resolve. These estimates vary by individual metabolism, age, and overall health.
Why do hangovers get worse with age?
Several factors compound with age. Liver enzyme production declines, slowing acetaldehyde breakdown. Body water percentage drops, concentrating alcohol in a smaller volume. Recovery processes across every organ system slow down. The same number of drinks hits harder at 45 than at 25 — higher peak BAC, longer exposure to toxic byproducts.