Estimate blood alcohol concentration (BAC) from the drinks you entered, your body weight, sex, and how long it has been since the first drink. The result is a Widmark estimate with a simple hourly fade toward 0% — useful for learning how dose, body size, and time interact, not for deciding whether someone is safe to drive.
How to interpret the estimate
The safety label deliberately does not say that a person “appears normal” or is safe at a low estimate. NHTSA says even small amounts of alcohol can affect driving, and people can be too impaired to drive before they look or feel drunk. At high levels, NIAAA warns that confusion, vomiting, seizures, slow or irregular breathing, difficulty remaining conscious, and pale or bluish skin can signal an alcohol overdose. Call emergency services if an overdose is suspected and do not leave an unconscious person alone.
This tool also assumes all entered alcohol has been absorbed, then subtracts a constant hourly rate from the time of the first drink. Real absorption and elimination do not follow that simple timeline exactly, so the “time to zero” output is not a countdown for driving, work, medication, or legal decisions.
Examples
Default: 155 lb man, two 12 oz 5% beers, 2 hours
Two 12 oz beers at 5% ABV are 1.2 oz of alcohol. Peak BAC is about 0.055%. After two hours at 0.015%/h the estimate is 0.025%, with around 2 more hours to reach the model's 0% estimate.
Same drinks, 155 lb woman
The female r factor (0.66 vs 0.73) raises the same 1.2 oz of alcohol to a peak near 0.060%. Two hours later the estimate is 0.030%, with around 3 more hours to the model's 0% estimate.
One 12 oz 5.8% beer, 80 kg man, just finished
At time zero the estimate is 0.027%, reaching the model's 0% estimate in a little under 2 hours. A 1 L 5% beer contains much more alcohol than the 12 oz serving and produces a substantially higher estimate.
Formula
The simplified US Widmark form used here is:
oz_alcohol = servings × serving_fl_oz × (ABV / 100)
r = 0.73 if male, 0.66 if female
BAC% = (oz_alcohol × 5.14) / (weight_lb × r) − 0.015 × hours
Pounds use the conversion.js factor 1 lb = 0.453592 kg. Kilograms and
grams are converted to pounds before the formula. BAC below zero is shown
as 0%. Hours remaining to 0% are BAC / 0.015, rounded up.
Labeled-ounce servings use the ounce on the label. Milliliter-only servings use 1 US fl oz = 29.573515625 mL. The calculator multiplies beverage volume by ABV; a larger or stronger pour can contain more than one standard drink.
This is an educational estimate, not a breathalyzer, a medical diagnosis, or legal advice. If you have been drinking, do not drive. Impairment can start well below 0.08%, and only a properly administered test measures BAC for legal purposes.