BAC Calculator — Blood Alcohol Content
Estimate your Blood Alcohol Content (BAC) using the Widmark formula. Calculate how long until you're sober. For educational use only — never drink and drive.
Estimated BAC
0.000%
BAC Effects Reference
0.01–0.05%Mild relaxation, slight impairment begins
0.06–0.10%Clearly impaired, illegal to drive (≥0.08%)
0.11–0.20%Slurred speech, severe coordination loss
0.21–0.40%Unconsciousness, life-threatening
Frequently Asked Questions
- BAC uses the Widmark formula: BAC = (Alcohol in grams) ÷ (Body weight in grams × r) × 100, where r = 0.73 for men and 0.66 for women (distribution ratio). Subtract the elimination rate: 0.015% per hour elapsed. Example: 170 lb man, 2 standard drinks in 1 hour → BAC ≈ 0.038% after elimination.
- In the US, one standard drink contains 14 grams (0.6 oz) of pure alcohol: 12 oz regular beer (~5% ABV), 5 oz wine (~12% ABV), or 1.5 oz distilled spirits (~40% ABV). Many craft beers (7–12% ABV) or large pours count as 1.5–2 standard drinks. Knowing this is key to accurate BAC estimation.
- The federal and all state legal limit for driving is 0.08% BAC (Blood Alcohol Content) for adults 21+. For commercial drivers, the limit is 0.04%. For drivers under 21 (zero-tolerance laws), the limit is 0.00–0.02% depending on the state. Utah has a stricter 0.05% limit. Driving impairment begins well below 0.08%.
- The liver eliminates alcohol at a rate of approximately 0.015% BAC per hour (one standard drink per hour). A BAC of 0.08% takes about 5–6 hours to reach 0.00%. A BAC of 0.15% takes ~10 hours. Nothing speeds up elimination — not coffee, food, cold showers, or exercise. Only time works.
- Women typically have a lower body water percentage (55%) vs. men (68%), resulting in a lower Widmark r-factor (0.66 vs. 0.73). The same amount of alcohol is distributed in less body water in women, producing a higher BAC. Women also produce less alcohol dehydrogenase (ADH) in the stomach, so more alcohol enters the bloodstream.
- Yes. Food slows alcohol absorption from the stomach into the bloodstream, reducing the peak BAC by up to 50% and delaying the peak by 1–2 hours. High-fat, high-protein foods (cheese, meat) are most effective. However, food doesn't reduce the total amount of alcohol processed — the total BAC area under the curve remains similar.
- BAC effects by level: 0.02–0.05%: Relaxation, mild impairment. 0.06–0.10%: Euphoria, clearly impaired judgment. 0.11–0.20%: Slurred speech, poor balance, high accident risk. 0.21–0.30%: Confusion, vomiting, blackout risk. 0.31–0.40%: Loss of consciousness, life-threatening. 0.40%+: Potentially fatal respiratory failure.
- This calculator provides an estimate only, not a medically precise BAC. Actual BAC varies based on genetics, liver health, medications, fatigue, hydration, and absorption rate. Many factors not accounted for here can raise or lower BAC significantly. Never use this to decide whether it is safe to drive. Always err on the side of caution.