Blood Alcohol (BAC) Calculator
Estimate your blood alcohol concentration in % (BAC) with the Widmark formula — NIAAA standard drinks, elimination over time, and where you stand against the 0.08% limit (0.05% in Utah). Never a clearance to drive.
Key facts
- Legal limits: 0.08% BAC (g/dL) in every US state except Utah, which has enforced 0.05% since Dec 30, 2018. Impairment starts well below that — judgment and reaction time measurably decline from about 0.02%.
- The same two standard drinks hit very differently: a 170 lb male computes to ~0.053% BAC (already over Utah's 0.05% limit), a 140 lb female to ~0.080% — right at the legal limit.
- The body eliminates only about 0.015% BAC per hour — coffee, water or a cold shower change nothing. From 0.101% (e.g. a 180 lb male after 4 beers) it takes ~1.4 hours to get below 0.08% and ~6.7 hours to reach 0.00%.
FAQ
- How accurate is this BAC calculator?
- It is an estimate. The Widmark formula is an approximation; real BAC depends on stomach contents, drinking duration, medication, metabolism and more, and can differ substantially. Only a measurement is reliable — never use the result to decide whether to drive.
- What is a standard drink?
- In the US, one standard drink contains 14 g of pure alcohol per NIAAA: 12 oz of beer (5% ABV), 5 oz of wine (12% ABV) or a 1.5 oz shot of spirits (40% ABV / 80 proof). Stronger beers (IPAs) or larger pours count for more.
- When can I drive again?
- The calculator CANNOT answer this. The shown elimination time is rough guidance — not a measurement and not a clearance. Impairment begins well below 0.08%, and impaired driving is an offense below any limit too. If you have been drinking, do not drive.