How blood alcohol content (bac) estimator works
Enter your body weight and sex, then list each drink with its volume (in milliliters or ounces) and ABV (alcohol by volume, as a percent). The tool converts each drink to grams of pure alcohol using ethanol's density (0.789 g/mL) and adds them up.
The estimate uses the Widmark formula: BAC (%) = (alcohol grams ÷ (body weight in grams × a sex factor)) × 100. The sex factor is roughly 0.68 for males and 0.55 for females, reflecting average body water. The result is the theoretical peak BAC if all the alcohol were absorbed at once.
Because the body metabolizes alcohol at about 0.015 %BAC per hour, the tool subtracts that amount for every hour since your first drink and clamps the result at zero. This is only an informational estimate — actual BAC varies with metabolism, food, health, medication, and many other factors, so never use it to decide if it is safe to drive.
Frequently asked questions
Is this BAC estimate accurate?
No. It is a rough informational estimate based on the Widmark formula and an average metabolism rate. Real BAC depends on body composition, food intake, liver function, medication, fatigue, and how fast you drank. Only a calibrated breathalyzer or blood test measures actual BAC.
What is a standard drink?
In the US a standard drink is about 14 grams of pure alcohol — roughly 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits. The tool reports how many standard drinks your entered drinks add up to so you can sanity-check the total.
Why does weight and sex matter?
Alcohol distributes through body water, so a larger person dilutes the same amount of alcohol more. On average females carry less body water than males of the same weight, which is why the Widmark sex factor differs (about 0.55 vs 0.68). These are population averages, not a measure of any individual.
Can I use this to decide if I'm okay to drive?
Never use this tool to decide whether it is safe or legal to drive. Even small amounts of alcohol can impair reaction time and judgment, and the legal limit varies by country and situation. If you have been drinking, use a designated driver, taxi, or rideshare instead.
