BAC Calculator

The Widmark formula: BAC% = (grams of alcohol ÷ (body weight kg × r × 10)) − (0.015 × hours elapsed). The r factor is 0.68 for men and 0.55 for women, reflecting differences in body water distribution (women have proportionally less total body water). Grams of alcohol = drinks × ml × ABV% × 0.789 (density of ethanol).

Legal limits vary: USA, Canada, Australia: 0.08% (80 mg/dL). UK: 0.08% England/Wales/NI; 0.05% Scotland. Most of Europe (Germany, France, Italy): 0.05%. Sweden, Norway, Poland, Japan: 0.02%. UAE, Saudi Arabia: 0.00% (zero tolerance). Always check your local jurisdiction — these limits change.

BAC decreases at a roughly constant rate of 0.015% per hour (range 0.010–0.020% depending on the individual, liver health, and genetics). Coffee, cold showers, energy drinks, and food after drinking do NOT speed elimination — only time works. A BAC of 0.08% takes about 5–6 hours to reach zero.

Two main reasons: (1) Women typically have lower total body water (55% vs 68% for men), so alcohol is more concentrated in a smaller volume. (2) Women have lower levels of alcohol dehydrogenase (ADH), the enzyme that begins metabolising alcohol in the stomach, so more alcohol reaches the bloodstream intact.

No — and you should never rely on any BAC calculator to decide whether to drive. The Widmark formula is an estimate with individual variation of ±20–30%. Genetics, liver health, medications, food intake, and tolerance all affect real BAC. If you've been drinking, the safe choice is always not to drive.