How to use this BAC calculator
Enter your weight and sex. Then add each drink you had: what it was, how big it was, how strong it was (the % on the label), and what time you finished it. The calculator shows your estimated BAC right now, when it will peak, and a graph of how it rises and falls over time.
You can add drinks as you go or enter them all afterward. Give each drink its own time (as close as you can remember). If you put them all at the same time, the estimate will be off.
Why our BAC calculator asks for size and strength
“One drink” can mean very different amounts of alcohol. A 12 oz beer at 10% has twice the alcohol of a 12 oz beer at 5%. And a heavy pour of wine has more than a light one. Entering size and strength gives a better estimate than just counting drinks.
For reference: one U.S. standard drink is about a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, or a 1.5 oz shot of 40% ABV. Our guide to standard drink sizes has more examples, and the standard drink calculator counts them for any drink.
How the BAC calculator works
It uses the Widmark formula, the standard method for estimating blood alcohol. Each drink's size and ABV are turned into grams of alcohol. That alcohol spreads through the water in your body, which depends on your weight and sex, so the same drink raises a smaller person's BAC more.
Drinks are absorbed over time, not all at once, so your BAC keeps rising for a while after your last drink. At the same time your liver clears about 0.015% BAC per hour (a little faster for women). The graph adds up every drink this way to show your BAC hour by hour.
Legal BAC limits
It is illegal to drive at 0.08% BAC or higher in most U.S. states. Utah's limit is 0.05%, and commercial drivers are held to 0.04%. You can still be charged below these limits if you are impaired. See the BAC chart for how many drinks reach each level, and jail time and BAC for DUI penalties.
Want to learn more? Read how a BAC calculator works, what is one drink and how many are in a bottle, how much alcohol is in common drinks, how long being drunk lasts, or about this calculator for the details.
BAC calculator FAQ
What is BAC?
BAC (blood alcohol concentration) is how much alcohol is in your blood. A BAC of 0.08% means 0.08 grams of alcohol in every 100 milliliters of blood.
How many drinks does it take to reach 0.08?
Over one hour, about 4 regular beers bring a 160 pound man to 0.08, and about 3 bring a 160 pound woman there. Lighter people get there with fewer. Enter your own weight and drinks above for your estimate.
How long does it take for BAC to go back to zero?
Your body clears about 0.015% BAC per hour, and nothing speeds it up. From 0.08, that is about 5 hours. The calculator shows the time your BAC should reach zero.
How accurate is a BAC calculator?
It is an estimate. Even with exact inputs, people differ, so your real BAC can be about 20 to 25% higher or lower near the peak. Food in your stomach lowers and delays the peak. Only a blood test or a calibrated breathalyzer measures BAC.
Can I use this calculator to decide if I can drive?
No. You can be impaired and charged with a DUI below the legal limit, and the estimate can be off. If you have been drinking, get a ride.
Does the calculator save my information?
Your weight and drinks stay in your own browser. They are not sent to or stored on our servers.