Estimate your blood alcohol content (BAC) based on your weight, sex, number of drinks, and time elapsed. See how long until you're back to 0.00%.
BAC impairment levels
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This blood alcohol calculator uses the Widmark formula, the most widely accepted method for estimating blood alcohol content. The formula accounts for the amount of pure alcohol consumed, your body weight, a sex-based body water constant (men have more body water than women, diluting alcohol more), and the rate at which your liver metabolizes alcohol (approximately 0.015% per hour).
One "standard drink" in the United States contains about 0.6 fluid ounces (14 grams) of pure alcohol. This is roughly equivalent to a 12-oz beer at 5% ABV, a 5-oz glass of wine at 12% ABV, or a 1.5-oz shot of spirits at 40% ABV. Cocktails and craft beers often contain more alcohol than a standard drink.
Your liver metabolizes alcohol at a relatively constant rate of about 0.015% BAC per hour — roughly one standard drink per hour. Nothing speeds this up: not coffee, cold showers, food, or exercise. These may make you feel more alert, but they do not lower your BAC.
At a BAC of 0.08% (the legal limit in 49 states; Utah is stricter at 0.05%), it takes approximately 5.3 hours to reach 0.00%. At 0.15%, it takes about 10 hours. Planning ahead and allowing enough time is the only way to ensure you're sober before driving.
In 49 US states, the legal limit is 0.08% BAC for drivers aged 21 and over; Utah is stricter at 0.05% (effective December 2018). For commercial drivers, the limit is 0.04%. For drivers under 21, most states have zero-tolerance laws (0.00%–0.02%). Even below the legal limit, alcohol impairs reaction time and judgment.
Women typically have a higher body fat percentage and lower body water content than men of the same weight. Since alcohol is water-soluble, it becomes more concentrated in a body with less water. Women also tend to have less alcohol dehydrogenase, the enzyme that breaks down alcohol in the stomach.
Eating before or while drinking slows alcohol absorption, which means your BAC rises more slowly and may peak at a lower level. However, eating after you've already absorbed the alcohol does not lower your BAC — your liver still needs the same amount of time to process it.
BAC calculators provide estimates within a reasonable range for most people. However, actual BAC varies based on genetics, liver health, medications, food intake, hydration, and individual metabolism. This tool should never be used to determine whether you are safe to drive. When in doubt, don't drive.