Blood Alcohol Content Calculator

Blood alcohol content measures how much alcohol is in your bloodstream, expressed as a percentage by volume. It is the number that legal driving limits are written around — 0.08 percent in the United States and much of the world, lower in many European countries and zero for new and professional drivers. This calculator estimates it with the Widmark formula, the standard model used for decades.

The formula has three moving parts. The alcohol you have consumed, converted to a standard unit of pure ethanol. Your body weight, since a larger body dilutes the same dose across more water. And a distribution factor that differs by sex, because men's bodies contain proportionally more water than women's at the same weight, so alcohol is diluted further. On top of that, the body clears roughly 0.015 percent per hour, which is subtracted for the time elapsed.

Read the state labels as rough descriptions rather than a diagnosis. At 0.02 percent most people notice little, around 0.05 judgement and coordination begin to slip, at 0.08 driving ability is clearly compromised, and above 0.15 the impairment is serious. But individual tolerance, food in the stomach, medication, fatigue and how fast the drinks were consumed all change the real effect on any single person.

The single most important thing to say about this tool is that it must never be used to decide whether to drive. Widmark gives an estimate with a wide margin of error and cannot account for your metabolism, whether you actually ate, or what medication you are taking. If you have been drinking, do not drive — full stop. The intended use here is educational: to show how quickly BAC rises with each drink and how slowly those 0.015 percent per hour tick it back down, so the arithmetic stops feeling abstract.

This calculator returns estimates for general information only. It is not medical advice, diagnosis or treatment, and it cannot replace an assessment by a qualified health professional. Individual results vary, and figures such as calorie needs, body-fat percentage and heart-rate zones are approximations based on population averages rather than measurements of you.