BAC Calculator

How to use

1. 1Pick your body type for the Widmark r value (male 0.68 or female 0.55) and enter your body weight in pounds or kilograms. Switching units converts the typed value so your body mass stays the same.
2. 2Enter how many hours have passed since your first drink. The tool subtracts linear elimination over that window.
3. 3Add each drink with its volume (oz or ml) and ABV percentage, or tap a Quick add preset like Regular beer, Wine, Shot of spirit, or Hard seltzer to add a fully filled drink in one tap.
4. 4Read your estimated BAC right now, the peak BAC at your last drink, and the total grams of alcohol consumed. The result is colored according to the typical effect band.
5. 5Check the legal limit table for the time until your BAC drops below 0.08, 0.05, 0.04, and 0.02 percent. Open Advanced to fine tune the elimination rate or to plug in your own Widmark r.
6. 6Tap Copy summary to share the breakdown, the legal limit timing, and the safety note as plain text.

About this tool

BAC Calculator estimates Blood Alcohol Content from a list of drinks using the Widmark formula, the same pharmacokinetic model used in clinical literature, NIAAA materials, and most state DUI training. For each drink you enter the volume and alcohol by volume (ABV) percentage; the tool converts that to grams of pure ethanol using the standard density of 0.789 g/ml, totals the grams across the session, and divides by body water mass (body weight times the Widmark r distribution ratio) to get the peak BAC right after the last drink. It then subtracts linear elimination (beta times hours elapsed, default 0.015 percent per hour) to estimate your BAC right now, and projects how long until the level drops below zero and below four common U.S. legal limits (0.08 in most states, 0.05 in Utah, 0.04 for commercial drivers, and 0.02 for drivers under 21). Widmark r defaults to 0.68 for assigned-male anatomy and 0.55 for assigned-female anatomy, the values used in NHTSA training, with an override field if you prefer a Forrest or Watson estimate of your own. A preset bar covers the U.S. standard drink set (12 oz beer at 5%, 5 oz wine at 12%, 1.5 oz of 40% spirit), light beer, craft beer, hard seltzer, sake, and overproof spirits, so you can build out a real-world session in a few taps. The tool runs entirely in your browser: drink list, weight, and timings are never uploaded. This is an estimate only, not a measurement. The Widmark formula is a population average and real BAC varies with food, hydration, medication, genetics, and other factors. It is not a breathalyzer and is not a defense against a DUI charge. Never drive after drinking; when in doubt, do not drive.

Free to use. Works in your browser. No signup, no login.