BAC calculator to estimate blood alcohol content from drink volume, ABV, body weight, sex, and time since drinking started using the Widmark formula.
Use this BAC calculator to estimate blood alcohol content from the total drink amount, alcohol by volume (ABV), body weight, sex, and time since drinking started. The calculator uses the Widmark formula and lets you switch the result between common BAC units.
This page is best for quick BAC estimates after beer, wine, spirits, cocktails, or any drink where you know the volume and strength. The result is only a rough estimate because real blood alcohol concentration can also be affected by food intake, metabolism, medications, hydration, body composition, and how quickly the drinks were consumed.
Enter your values to see the estimated BAC range.
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Widmark formula
$$BAC \approx \frac{A}{r \times W} - \beta \times t$$
A = pure alcohol in grams,
W = body weight in kilograms,
r = Widmark distribution factor,
t = hours since drinking started,
β = alcohol elimination rate used for the estimate.
This calculator uses the Widmark approach for a rough estimate only. Actual BAC can vary because of food intake, metabolism, medications, body composition, and drinking pattern.
Sources: Hustad JT, Carey KB (2005); Peck RC et al. (2008).
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BAC Calculator FAQ
BAC means blood alcohol content or blood alcohol concentration. It is usually expressed as the amount of alcohol present in the blood, often as a percentage or per mille value.
This calculator estimates BAC with the Widmark formula. It combines the total amount of alcohol consumed, your body weight, sex, and the time since drinking started, then applies an estimated alcohol elimination rate.
No online blood alcohol calculator can be exact for every person. Food, metabolism, medication, body composition, health conditions, and drinking speed can change the real result, so treat the number as an estimate only.
No. Coffee, water, food, and cold showers may change how you feel, but they do not reliably reduce BAC. Time is the main factor that lowers blood alcohol concentration.
No. Legal BAC limits vary by country, state, vehicle type, age, and license status. Do not rely on an online BAC estimate to decide whether it is safe or legal to drive.
Not automatically. They are only roughly equivalent if the cocktail contains about the same amount of pure alcohol as the shot. A 4 cl shot at 40% contains about 12.6 g of pure alcohol. A gin and tonic, rum and cola, or mojito can be similar if it uses roughly one 4 cl measure of 40% spirit, but the real amount depends on the recipe and pour size.
