BAC Calculator
Estimate your blood alcohol content, see when you will be legally sober, and compare legal limits worldwide.
About this tool
Estimate your blood alcohol content using the Widmark formula. Enter your weight, sex, number of drinks, and time to see your estimated BAC, a color-coded gauge, and how long until you are legally sober. Includes legal BAC limits for major countries.
How to use it
Quick steps to get the most out of this utility.
- 1
Enter your details
Select your sex and enter your body weight in lbs or kg.
- 2
Add your drinks
Set the number of standard drinks consumed — use the +/− buttons or type directly.
- 3
Set the time
Enter how long you took to consume those drinks and the total time since your first drink.
- 4
Read your BAC
See your estimated BAC, the color-coded gauge, how long until you are sober, and compare legal limits worldwide.
About the Widmark Formula
The BAC calculator uses the Widmark formula, one of the most widely used methods for estimating blood alcohol content. The formula accounts for the total alcohol consumed, body weight, and a gender-specific distribution factor (men have a higher proportion of body water than women, diluting alcohol more effectively). The result is then reduced by a standard metabolism rate of 0.015 BAC per hour.
The estimates provided by this tool are approximations. Actual BAC can vary significantly based on individual factors including genetics (particularly the ADH and ALDH enzyme variants), liver health, whether you ate food, medications, hydration status, and even menstrual cycle phase. This tool is intended for educational purposes only — never use it to decide whether it is safe to drive after drinking.
Frequently asked questions
How is BAC calculated?+
This calculator uses the Widmark formula: BAC = (A × 5.14 / (W × r)) − 0.015 × H, where A is total alcohol in ounces, W is body weight in pounds, r is the distribution factor (0.68 for men, 0.55 for women), and H is hours since first drink.
What is a standard drink?+
A standard drink in the US contains approximately 0.6 oz of pure alcohol, which is found in: 12 oz of beer (5% alcohol), 5 oz of wine (12% alcohol), or 1.5 oz of spirits (40% alcohol). This calculator treats all three as one standard drink.
When will I be legally sober?+
The calculator estimates time to reach 0.00% BAC using an average metabolism rate of 0.015 BAC/hr. However, alcohol metabolism varies significantly between individuals based on genetics, liver function, food intake, medications, and other factors. Always err on the side of caution.
What is the legal BAC limit for driving?+
In most US states, the legal limit is 0.08%. Many countries have lower limits: 0.05% in Australia, Germany, and Japan; 0.02% in Sweden, Norway, Russia, and China. Commercial drivers typically face stricter limits.
Can BAC continue to rise after I stop drinking?+
Yes. Because alcohol must be absorbed through the stomach and small intestine before entering the bloodstream, BAC can continue to rise for 30–90 minutes after your last drink, depending on how much food is in your stomach.
Does food affect BAC?+
Yes. Eating food, especially carbohydrates and fats, slows alcohol absorption, lowering peak BAC compared to drinking on an empty stomach. This is why the calculator factors in time — the longer the drinking period, the more your body processes alcohol.
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