Blood Alcohol (BAC) Calculator
Estimate blood alcohol concentration from drinks, body weight and time.
Results update as you type.
About this calculator
A blood alcohol content (BAC) calculator estimates the alcohol in your bloodstream using the Widmark formula, from the number of standard drinks, your body weight and sex, and the time since your first drink. It is an educational estimate only — many factors change real BAC, so never use it to decide whether to drive.
Frequently asked questions
What is the Widmark formula?
BAC% = (grams of alcohol ÷ (body-weight grams × r)) × 100 − 0.015 × hours, where r is the distribution ratio (about 0.68 for men and 0.55 for women) and 0.015 is the percent of alcohol eliminated per hour.
Is this accurate enough to decide if I can drive?
No. Real BAC depends on food, hydration, medication, drink strength and individual metabolism, and the estimate can easily be off. If you have been drinking, do not drive — this tool is for education only.
How long until my BAC returns to zero?
The body clears alcohol at roughly 0.015 percent per hour regardless of coffee, water or a cold shower. The calculator divides your current BAC by that rate to estimate the sober-up time.
Results are estimates for general guidance only, not financial, medical or tax advice.