Why this exists, and what it isn't for
Understanding roughly how alcohol moves through the body — and how slowly it actually clears — can help people grasp why "sobering up fast" tricks (coffee, cold showers, food) don't work: the liver eliminates alcohol at a fixed, slow rate no matter what you do. That's useful to understand. It is not useful, and not the intent here, as a way to calculate a number low enough to feel comfortable driving.
Frequently asked questions
Why does this estimate have such a wide margin of error?
The Widmark formula was developed decades ago from population averages — real individual results are shifted by food intake, medications, drinking speed, hydration, and genuine metabolic differences between people. Research on the formula's accuracy cites error margins of around ±20-30% in practice.
Does staying under the legal limit mean I'm not impaired?
No. Reaction time, judgment, and coordination measurably decline starting well below most legal driving limits. The legal limit reflects a policy line, not a safety threshold — impairment exists on a continuum starting from the first drink.
What should I actually do if I've been drinking and need to get somewhere?
Use a rideshare service, call a taxi, ask a sober friend or family member, or simply stay where you are. None of these options require knowing an exact BAC number.
This calculator provides a rough educational estimate only, using the Widmark formula, and is not a measurement of actual blood alcohol content. It should never be used to decide whether driving, operating machinery, or any safety-critical activity is acceptable after drinking.