Blood Alcohol (BAC) Calculator
Free blood alcohol calculator: estimate your BAC from drinks, body weight, sex and time with the Widmark formula, and how long until it is back to zero.
What it does
Blood alcohol concentration (BAC) is the amount of alcohol in your blood. This calculator estimates it with the Widmark formula: the grams of pure alcohol you drank divided by your body weight and a body water factor (0.68 for men and 0.55 for women), minus about 0.015% for each hour since you started drinking. Food, medicines, health and drinking speed change the real value a lot, so it is only an estimate.
How to use it
- Choose your units and sex and type your weight.
- Choose the drink (or type its size and alcohol content) and how many you had.
- Type how many hours have passed since the first drink.
These are estimates for healthy adults and do not replace advice from a doctor, dietitian or coach. The calculation runs in your browser.
Frequently asked questions
What is the legal limit for driving?
It varies by country: 0.08% (0.8 g/L) in most of the US and in England, 0.05% (0.5 g/L) in most of Europe and in Australia, and zero or close to zero in several countries and for new drivers. Even below the limit, alcohol slows reactions.
What is a standard drink?
In the US, 14 g of pure alcohol: about a 12 oz beer at 5%, a 5 oz glass of wine at 12% or 1.5 oz of spirits at 40%. Other countries use 8 g (UK unit) or 10 g.
Can coffee or a shower sober me up?
No. The liver removes alcohol at a roughly fixed rate, about 0.015% an hour, and nothing speeds it up. Coffee can make you feel more awake while the alcohol is still there.
Why is BAC higher in women after the same drinks?
On average women have less body water per kilogram, so the same alcohol is less diluted. That is why the Widmark factor is lower for women.
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NIAAA — What is a standard drink?
Wikipedia — Blood alcohol content (Widmark formula)