What is a hangover and why does it happen?
A hangover is a collection of unpleasant symptoms that occur after drinking too much alcohol. The primary causes include dehydration (alcohol is a diuretic, causing your body to expel 120–160 ml more fluid per drink than it takes in), acetaldehyde buildup (a toxic byproduct of alcohol metabolism), disrupted sleep quality, and inflammation of the stomach lining. Hangover severity is closely tied to your peak blood alcohol concentration (BAC), hydration levels, and whether you ate food while drinking.
How long does a hangover last?
The average hangover lasts about 12–18 hours after you stop drinking, though severe hangovers can persist for up to 72 hours. Duration depends on how much you drank, your body weight, biological sex, hydration, and sleep quality. The body metabolizes alcohol at a fairly constant rate of about 0.015% BAC per hour — roughly one standard drink per hour. Once your BAC reaches zero, hangover symptoms typically begin to fade, though dehydration and sleep disruption effects can linger. Use our BAC calculator for a detailed blood alcohol estimate.
What is the Widmark formula for BAC?
The Widmark formula estimates peak blood alcohol concentration: BAC = (alcohol in grams) / (body weight in kg × r × 10), where r is the Widmark factor (0.68 for males, 0.55 for females). A standard drink contains about 14 grams of pure alcohol. For example, a 70 kg male who had 4 standard drinks: BAC = (4 × 14) / (70 × 0.68 × 10) = 56 / 476 = 0.118‰. The elimination rate is then subtracted: roughly 0.015‰ per hour since the last drink.
What factors make a hangover worse?
Several factors increase hangover severity beyond just the number of drinks. Drinking on an empty stomach allows faster alcohol absorption, raising peak BAC by up to 20%. Dehydration compounds symptoms — each drink creates a fluid deficit, and failing to drink water between alcoholic beverages worsens headaches and fatigue. Dark spirits (whiskey, bourbon, red wine) contain higher levels of congeners, byproducts of fermentation that intensify hangover symptoms. Age also plays a role, as liver enzyme efficiency decreases over time. Our water intake calculator can help you understand your daily hydration needs.
What is hangxiety and why does alcohol cause anxiety?
Hangxiety — hangover-related anxiety — is one of the most reported but least understood hangover symptoms. Alcohol boosts GABA activity in the brain, producing feelings of relaxation and lowered inhibition. As your body metabolizes alcohol, the brain compensates by reducing GABA and increasing glutamate, an excitatory neurotransmitter. This rebound effect creates a heightened state of anxiety, restlessness, and racing thoughts that typically peaks 10–14 hours after your last drink. Research suggests people who are naturally shy or socially anxious experience more severe hangxiety. Staying hydrated, sleeping enough, and eating before drinking all help reduce the neurochemical imbalance that triggers it.
Does drinking water or eating food reduce hangover severity?
Yes, both help significantly. Eating food — especially before and during drinking — slows alcohol absorption in the stomach, effectively reducing your peak BAC by up to 20–30%. Carbohydrate-rich and fatty foods are particularly effective. Drinking water between alcoholic drinks combats dehydration, the primary cause of hangover headaches. A good rule of thumb is to drink at least one glass of water for every alcoholic beverage, and an extra glass before bed. While neither food nor water can prevent a hangover entirely, they meaningfully reduce severity and recovery time.
How does this hangover calculator work?
This calculator uses the Widmark formula to estimate your peak and current BAC based on the number of standard drinks, your body weight, and biological sex. It then calculates recovery time by dividing your current BAC by the average elimination rate of 0.015‰ per hour. Hangover severity is scored based on peak BAC with adjustments for food intake and hydration — water reduces the severity score, and eating while drinking lowers effective peak BAC by 30%. The water deficit shows how many more glasses you should drink based on a recommendation of 1.5 glasses per alcoholic drink. Track your sleep cycles for better recovery.