Free BAC calculator
BAC Calculator
Enter drink size, ABV, body weight, sex, and time since your first drink. Use beer, wine, liquor, or a custom drink to estimate current BAC, time to zero, and a legal-threshold comparison.
Example runs
Common BAC examples
These examples use the same kind of inputs as the calculator. They are here to help you sanity-check the scale of a result, not to replace your own calculation.
Dinner with wine
0.049%Female · 140 lbs
2 glasses of wine over 2h
Below many limits, but impairment is still possible
Two beers after work
0.018%Male · 180 lbs
2 beers over 2h
Low estimate, not proof of safe driving
Several drinks quickly
0.117%Male · 160 lbs
5 liquor shots over 2h
Above the common 0.08% legal limit
Estimate your BAC
Start with the drink details that change the result
Enter what was consumed, when drinking started, and the driving limit you want to compare against. The result shows an estimate and the time window around it.
Enter body inputs
Choose sex, body weight, and the legal limit you want the result compared against.
Count actual alcohol
Add beer, wine, liquor, or a custom drink. Adjust serving size and ABV when the pour is not standard.
Read the timeline
Review estimated current BAC, peak BAC, time to zero, time below the selected limit, and the BAC curve.
Make sense of the result
After you calculate, answer the next question
A BAC number is only useful if you know how to read it. Use these references to compare it with a chart or check a legal threshold.
Compare against a BAC chart
Use the BAC chart when you want a quick drinks-by-weight reference instead of exact serving inputs.
Open BAC chartCheck legal limit context
Compare common country limits after you have an estimate, especially if the result is near a threshold.
Compare limitsTrust the estimate carefully
Assumptions behind this BAC calculator
BAC estimates are only as good as the inputs and assumptions. Treat the result as planning information, not a driving decision.
Formula
BACalc estimates BAC with the Widmark formula using body weight, sex, alcohol consumed, and elapsed time.
Elimination
The calculator subtracts 0.015% BAC per hour as an average alcohol elimination rate.
Privacy
Calculator inputs are handled in the browser and are not submitted to create a stored BAC record.
Legal limit sample
Selected BAC limits vary widely
Brazil
0.00%Japan
0.03%Germany
0.05%Australia
0.05%United States
0.08%BAC calculator FAQ
Can this bac calc make a driving decision for me?+
No. It can estimate BAC and compare it with a selected legal limit, but it cannot measure your actual impairment. Food, medication, sleep, health, and metabolism can all change your real-world ability to drive.
How fast does BAC go down?+
A common average is about 0.015% BAC per hour. Some people metabolize alcohol more slowly or more quickly, but time is the main factor that lowers BAC.
What counts as one standard drink?+
In the US, a standard drink contains about 0.6 oz or 14 grams of pure alcohol. That is roughly 12 oz beer at 5%, 5 oz wine at 12%, or 1.5 oz liquor at 40%.
Why do drink size and ABV matter?+
The calculator estimates pure alcohol consumed. A 16 oz craft beer at 7% contains much more alcohol than a 12 oz beer at 5%, and a large wine pour can count as more than one standard drink.
Does coffee, water, or a cold shower lower BAC?+
No. These may change how alert you feel, but they do not remove alcohol from your bloodstream faster. Your body needs time to metabolize alcohol.