Estimate blood alcohol content (BAC) using the Widmark formula. This is an educational estimate only — actual BAC varies by individual, and you should never drive after drinking regardless of the result.
A BAC Calculator provides an estimate of blood alcohol concentration based on the amount of alcohol consumed, body weight, gender, and the time elapsed since drinking began. It is commonly used to get a rough sense of impairment level, though it should never be treated as a precise substitute for a breathalyzer or blood test, and it should never be used as the sole basis for deciding whether it's safe to drive.
Most BAC estimators use the Widmark formula: BAC = (Alcohol consumed in grams divided by (Body weight in grams times distribution ratio)) x 100, minus (Elimination rate x hours elapsed). The distribution ratio (Widmark factor) is typically around 0.68 for men and 0.55 for women, reflecting average differences in body water content, and the average elimination rate is roughly 0.015% BAC per hour as the liver metabolizes alcohol.
Enter your gender, body weight, the number and type of standard drinks consumed, and the time period over which you drank. The calculator estimates your current BAC based on these inputs and the average elimination rate, though it always includes a strong reminder that individual results can vary significantly.
Example 1: A 70 kg man who consumes three standard drinks (each roughly 14 grams of pure alcohol) over two hours has an estimated BAC in the range of 0.03-0.04%, though this can vary with metabolism and food intake.
Example 2: A 60 kg woman consuming the same three standard drinks over the same two hours typically shows a somewhat higher estimated BAC, often in the 0.05-0.06% range, reflecting the lower average distribution ratio used for women in the formula.
Women generally have a lower percentage of body water relative to total body weight compared with men of similar weight, which means the same amount of alcohol becomes more concentrated in a woman's bloodstream, leading to a higher estimated BAC for identical inputs.
Food, especially fatty or protein-rich food, slows the rate at which alcohol is absorbed into the bloodstream, which can lower the peak BAC and spread out the effects over a longer period, though it does not change the total amount of alcohol eventually absorbed.
No, this is only a rough statistical estimate based on average population data; actual BAC is affected by many individual factors including metabolism, medication, food, hydration, and overall health, so this tool should never be used to judge fitness to drive.
Limits vary by country and sometimes by driver category (such as commercial or new drivers), commonly ranging from 0.00% to 0.08%, and it is always safest to avoid driving after any alcohol consumption rather than trying to stay just under a legal threshold.
Since the average elimination rate is about 0.015% per hour, a BAC of 0.06% would take roughly four hours to fully clear on average, though this varies from person to person and no method (coffee, cold showers, exercise) speeds up actual alcohol metabolism.
A standard drink is typically defined as containing about 14 grams of pure alcohol, which roughly corresponds to a small beer, a standard glass of wine, or a single shot of spirits, though actual alcohol content varies by beverage strength and serving size.
Yes, many medications interact with alcohol in ways that increase impairment or affect metabolism, independent of the calculated BAC number itself, so anyone on prescription medication should be especially cautious and consult their doctor or pharmacist about alcohol interactions.
Alcohol continues to be absorbed from the stomach and intestines into the bloodstream for some time after the last drink, so BAC can keep climbing for 30-60 minutes after drinking stops before the elimination process starts to bring it back down.
Yes, since alcohol distributes through body water rather than fat tissue, two people of the same total weight but different body fat percentages can reach different BAC levels from identical drinks, because the person with more lean mass has proportionally more body water to dilute the alcohol into.
No, regular drinkers can develop a tolerance that reduces how impaired they feel at a given BAC, but the actual blood alcohol concentration and the physical risks it carries, including impaired reaction time and judgment, remain the same regardless of how tolerant someone feels.