About BAC Levels

We are health researchers and developers who spent too long watching BAC calculators get the pharmacokinetics wrong in ways that matter.

The Widmark formula — published by Erik Widmark in 1932 and still the basis for every credible BAC estimate — requires accurate body water constants to produce useful output. Most tools online use the wrong constants, or apply the same constant regardless of sex, which produces errors of 15–20% in the estimate.

Our constants follow Watson's 1981 peer-reviewed body water research, which remains the standard reference in forensic pharmacokinetics. The female and male constants are different because the physiology is different, and that difference is not cosmetic — it changes the output meaningfully.

Beyond the formula, the other thing most tools ignore is time. BAC is not a static number. It peaks after absorption and declines at a rate that varies by body weight, food consumption, and how long ago the first drink was. We built the time curve into every calculation because a snapshot BAC at "right now" is less useful than understanding where the number is heading.

All legal BAC limits — federal guidance, per-state driving limits, and workplace standards — are sourced from official state statutes and NHTSA publications. We update them when state law changes.

No data leaves your browser. We have no server-side storage of any kind. The inputs you enter exist only in your session.

These tools are for informational and educational purposes. BAC estimates are approximations — individual metabolism varies, and no calculator replaces a breathalyzer or blood test. If you are making a decision about driving or safety, the only right answer is not to drink and drive, regardless of what any estimate shows.

Questions or data corrections: Contact us