BAC Calculator
Blood Alcohol Concentration (BAC) measures the percentage of alcohol in your bloodstream. This calculator uses the Widmark formula to estimate your BAC based on what you have drunk, your body weight, biological sex, and how much time has passed. Understand the effects at different BAC levels and when you may return to zero.
This is an estimate only. Never use this to decide if you are safe to drive. The only safe BAC for driving is 0.00%.
Your drinks:
About this calculator
This tool uses the Widmark formula to estimate BAC: total alcohol in grams is calculated as volume (ml) x ABV x 0.789 (ethanol density). BAC = (alcohol grams / (body weight in grams x Widmark r factor)) x 100 minus 0.015% per hour of metabolism. The r factor is 0.68 for males and 0.55 for females.
Individual BAC varies based on genetics, food intake, hydration, medications, liver health, and many other factors. This estimate can be significantly different from your actual BAC. The only way to know your true BAC is with a calibrated breathalyser or blood test.
Never rely on any calculator to determine if you are safe to drive or operate machinery. Impairment can occur at any BAC level. If you have been drinking, arrange alternative transport.
Responsible Drinking
Personal BAC testers, non-alcoholic alternatives, drink tracking apps, and alcohol-free spirits.
Some links may be affiliate links. If you make a purchase, we may earn a small commission at no extra cost to you.
Frequently Asked Questions
How is BAC calculated?
What BAC level is legally drunk?
How fast does alcohol leave your system?
Is this calculator accurate for driving decisions?
More Habits Tools
View all →Habit Tracker
Track up to 10 daily habits with a visual streak counter. Build consistency, monitor your longest streaks, and develop healthier routines over time.
Due Date Calculator
Calculate your estimated due date using Naegele's rule based on your last menstrual period or conception date. View your trimester timeline and key pregnancy milestones.
Period Calculator
Predict your next period, fertile window, and ovulation date based on your cycle history. View a 6-month menstrual cycle forecast.
Ovulation Calculator
Estimate your ovulation date and fertile window based on your menstrual cycle. View a 6-month fertility forecast to help you plan.
Related Tools
Alcohol Unit Calculator
Calculate alcohol units, calories, and estimated metabolism time for your drinks. Compare your intake to recommended weekly limits.
Water Intake Calculator
Calculate how much water you should drink daily based on your weight, activity level, and climate. Get a personalised hydration target in litres and glasses.
Sleep Calculator
Calculate optimal bedtimes and wake-up times based on 90-minute sleep cycles. Align your schedule to wake between cycles and feel more rested every morning.