BAC Calculator — Blood Alcohol Content

In the United States, the legal BAC limit for drivers 21 and older is 0.08% (0.08 g/dL). For commercial drivers it is 0.04%. For drivers under 21, it is 0.02% or lower in most states. Utah has the lowest limit at 0.05%. Canada and most European countries also use 0.08%, while many countries use 0.05% or even 0.00%. However, impairment begins well below 0.08% — reaction time, coordination, and judgment are all affected starting around 0.02–0.03%.

The liver metabolizes alcohol at a fairly constant rate of about 0.015–0.017% BAC per hour, regardless of body size, coffee, food, or exercise. There is no way to speed this up — "sobering up" tricks don't work. A BAC of 0.10% takes roughly 6–7 hours to reach 0.00%. At 0.15% you're looking at 9–10 hours. The only cure for high BAC is time. Sleep also does not accelerate metabolism — you may still be impaired in the morning after a heavy night of drinking.

Women typically reach higher BAC than men of the same weight after consuming the same amount of alcohol. This happens because women have a higher percentage of body fat (which doesn't absorb alcohol) and lower total body water, resulting in less dilution of alcohol in the bloodstream. Women also produce less alcohol dehydrogenase (the enzyme that breaks down alcohol) in the stomach. The Widmark formula uses different distribution ratios: 0.73 for men and 0.66 for women to account for this difference.