BAC calculator.
Use this free bac calculator to get fast estimates, compare scenarios, and understand the numbers with clear step-by-step context.
Use the BAC Calculator.
Results update automatically as you type. No account is required.
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About the BAC Calculator
Blood Alcohol Content (BAC) estimates the percentage of alcohol in your bloodstream. This tool uses the widely cited Widmark formula to give a rough idea of how drinks, body weight, sex, and time affect BAC. It is for general awareness only — never a substitute for good judgment about driving.
How it works
The Widmark estimate is BAC = (alcohol in grams ÷ (body weight in grams × r)) × 100 − 0.015 × hours, where r is a body-water constant (about 0.68 for men, 0.55 for women) and 0.015 is the average hourly elimination rate. One US standard drink contains about 14 g of pure alcohol.
Reading the chart
The band chart shows where the estimate falls relative to the 0.08% legal driving limit used in most regions, but real BAC varies widely with food, metabolism, and medication.
⚠ Safety warning: This is a rough estimate only and can differ greatly from your real blood alcohol level. Never use it to decide whether it is safe to drive. If you have been drinking, do not drive — arrange a taxi, rideshare, or designated driver.
FAQ
How accurate is this?
Not accurate enough to rely on. Food, hydration, medications, and individual metabolism can shift real BAC dramatically. Treat the number as a rough illustration.
How long until I am sober?
The body clears alcohol at roughly 0.015% BAC per hour and you cannot speed it up. Coffee, food, and cold showers do not lower BAC.
What is a standard drink?
About 14 g of pure alcohol — roughly a 12 oz regular beer, 5 oz of wine, or 1.5 oz of spirits. Many real-world pours are larger.