how many beers to fail a breathalyzer
The question assumes there is a "safe" number of beers before a breathalyzer flags you. In Brazil, that assumption is wrong: under article 165 of the Traffic Code, any detected alcohol concentration, even far below the crime threshold, already counts as an administrative infraction. This page opens the calculator with a 75 kg male profile already filled in; add the two beers from the example below to illustrate that.
Body weight goes directly into the Widmark formula, the same dose produces a much higher estimated BAC in someone who weighs less.
The individualized r factor (Watson/Forrest) shifts the estimate relative to the fixed sex-based factor (classic Widmark), especially outside the average body composition.
Classic Widmark uses a fixed distribution factor (r), 0.68 for men and 0.55 for women, a population average. The Watson/Forrest method computes an individualized factor from your estimated total body water, based on height and weight, divided by weight, which tends to be closer to reality for people whose body composition falls outside Widmark's average, for example in cases of obesity.
Yes, technically. Since the tolerance for the administrative infraction is zero, any alcohol concentration the breathalyzer detects, even a small one, already falls under article 165, after deducting the device's technical margin of error.
It could be enough time for full elimination, a genuinely small dose, or individual variation (weight, metabolism, whether they ate). None of those turn into a reliable rule like "X drinks is always safe", which is why the practical guidance remains: do not drink and drive.
This is an educational estimate, not a measurement of your real blood alcohol. Individual variation is large, and the tool does not know whether you ate, took medication, or have a different tolerance than average. In Brazil, the tolerance for the administrative infraction is zero from any detected alcohol concentration (CTB article 165). The only reliably correct decision after drinking is not to drive.
Watson/Forrest computes the distribution factor from your height and weight instead of using a fixed average per sex.
No drinks added yet. Add at least one to calculate BAC.
This number is not permission to drive. After drinking, do not drive, even with a low or zero result.
Add at least one drink to see the curve.
All the math runs in your browser. No profile or drink data is ever sent to a server.