Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Estimate blood alcohol content (BAC) using the Widmark formula.
0.035%
This tool estimates blood alcohol content (BAC) using the Widmark formula (1932), still the standard formula cited for BAC estimation, based on bodyweight, sex, standard drinks consumed, and time elapsed.
Enter your weight, sex, number of standard drinks, and hours since your first drink. Estimated BAC appears instantly.
BAC = (Alcohol Grams / (Body Weight(g) × r)) × 100 - (0.015 × Hours)
r (Widmark distribution ratio) = 0.68 for men, 0.55 for women. One US standard drink ≈ 14g pure alcohol. The 0.015/hour term accounts for average metabolism rate.
This is a rough estimate for informational purposes only -- never use it to judge whether you're safe to drive or perform any activity requiring sobriety. Actual BAC depends on many factors this formula doesn't capture (food intake, medication, individual metabolism, drink strength). If you've been drinking, don't drive -- use a designated driver, rideshare, or public transit.
Consider a hypothetical 180 pound man who has 2 standard drinks and it has been 1 hour since the first drink. Weight in grams is 180 x 453.592, about 81,647 g. Alcohol is 2 x 14 = 28 g. The distribution term is 81,647 x 0.68, about 55,520. Dividing gives 0.000504, times 100 is 0.0504, and subtracting 0.015 for the one hour leaves about 0.035 percent. Now a hypothetical 140 pound woman with 3 drinks after 2 hours: weight is about 63,503 g, alcohol is 42 g, the term is 63,503 x 0.55, about 34,927, giving 0.120 before the time adjustment, and after subtracting 0.030 the estimate is about 0.090 percent.
BAC % = (Drinks x 14 g / (Weight in g x r)) x 100 - (0.015 x Hours), never below 0
Two behaviors of this tool are worth noting. The result cannot drop below zero, so after enough hours it simply shows 0.000. And the time reduction is a straight line from your first drink, so it does not model the body absorbing alcohol over time.
The tool uses 14 grams of pure alcohol per drink. In the United States that is commonly described as about 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of 80 proof spirits. Craft beers, large wine pours, and mixed drinks with several shots often contain well over one standard drink, so count by actual alcohol content, not by the number of glasses. Entering "2" when you really had the equivalent of 3.5 understates the result.
Impairment begins before any legal limit is reached, and legal limits differ by country, state, and driver type. Because of the simplifications above, real BAC can be higher or lower than shown. Coffee, cold showers, or waiting a short time do not speed up elimination. If you have been drinking, arrange a sober driver, a taxi, or a rideshare. Check your local authority for actual legal limits rather than relying on a figure from a calculator.
If you or someone you know is concerned about their drinking, a doctor or a local support service can help. This tool is for education only.
No -- absolutely not. This is a rough educational estimate, not a precise measurement, and real BAC is affected by many factors this formula can't account for. Never use any calculator to judge fitness to drive.
The Widmark distribution ratio (r) reflects typical differences in body water percentage between sexes, which affects how alcohol distributes through the body.
Yes, significantly -- food slows alcohol absorption, which this formula doesn't account for, meaning actual BAC after drinking on a full stomach is typically lower than this estimate at a given time point.
The formula subtracts 0.015 for each hour elapsed and will not go below zero. Once the subtraction exceeds the initial figure, the tool displays zero.
The drinks field accepts steps of 0.5, so you can enter values like 2.5. Hours can be entered in quarter-hour steps such as 1.25.
No, weight is entered in pounds. Multiply kilograms by 2.2046 to convert before entering.
Not necessarily. Weight and sex enter the formula, and many other factors that it ignores also differ between people.
Reference: Centers for Disease Control and Prevention