BAC Calculator
Estimate your Blood Alcohol Concentration with a detailed drink database, projected BAC timeline, and US legal limit reference. Uses the Widmark formula for forensic-grade estimation.
Looking for a quicker estimate? Try our simpler Alcohol Calculator.
BAC Estimator
1.0 standard drinks per serving
How many servings of the selected drink
Weight in pounds
Determines the body water ratio used in the Widmark formula
How to Use This BAC Calculator
Choose Your Drink
Select from 18 pre-configured drinks with exact ABV and volume, or toggle custom mode to enter your own drink specs
Enter Your Details
Add your body weight (lbs or kg), biological sex, number of servings, and hours since your first drink
Review Your BAC Curve
See your current and peak BAC, time until sober, time until legally under the limit, and a projected timeline
US Legal BAC Limits
Standard Limit
Legal limit for drivers 21 and older in most states.
All 50 states and D.C. (standard for drivers 21+)
Commercial Drivers
Federal limit for commercial driver's license (CDL) holders nationwide.
Federal standard, all states
Under 21 (Zero Tolerance)
Most states enforce zero tolerance for underage drivers. Limits range from 0.00% to 0.02%.
All 50 states (varies: 0.00% in most, 0.02% in some)
Lower Limit States
Utah sets its general DUI threshold at 0.05% BAC, the lowest in the US.
Utah
Widmark Formula Details
BAC = (A / (W x r)) x 100 - (0.015 x t)This calculator converts your drink into grams of pure alcohol using the formula:
A (grams) = volume (oz) x 29.5735 (ml/oz) x ABV x 0.789 (g/ml density)Then the Widmark formula variables are:
- A = total grams of pure alcohol consumed
- W = body weight in grams (lbs x 453.592)
- r = Widmark factor: 0.68 for males, 0.55 for females
- t = hours since first drink
- 0.015 = average metabolic elimination rate (BAC% per hour)
The Widmark factor reflects the difference in total body water between biological sexes. Males average about 68% body water by weight, females about 55%. Since alcohol distributes through body water, a lower water ratio produces a higher BAC for the same amount of alcohol.
The metabolic elimination rate of 0.015% per hour is a population average. Individual rates range from about 0.010% to 0.020% per hour depending on genetics, liver health, and chronic alcohol exposure.
Frequently Asked Questions
How is this BAC calculator different from a simple alcohol calculator?
This BAC calculator provides a detailed drink database with exact ABV and volume for each beverage type, projects your BAC curve over time so you can see when you will be sober, and includes US legal limit references by state. A basic alcohol calculator typically only gives a single BAC number without the timeline or drink-level detail.
What is the Widmark formula?
The Widmark formula (BAC = A / (W x r) x 100 - beta x t) was developed by Erik Widmark in 1932 and remains the standard for forensic BAC estimation. It uses total grams of alcohol consumed (A), body weight in grams (W), a gender-based body water constant (r: 0.68 male, 0.55 female), and an average metabolic elimination rate (beta: 0.015% per hour) to estimate blood alcohol concentration.
How accurate is a BAC calculator?
BAC calculators provide estimates, not exact measurements. Actual BAC depends on factors the formula cannot capture: food in your stomach, hydration, liver health, medications, genetics, and the rate at which you consumed drinks. The only way to know your true BAC is with a calibrated breathalyzer or blood test. Never rely on a calculator to decide whether you are safe to drive.
What BAC level is legally drunk in the US?
In 49 states plus D.C., the legal per-se DUI limit for drivers 21 and older is 0.08% BAC. Utah sets its limit at 0.05%. Commercial drivers face a 0.04% federal limit. All states enforce zero-tolerance laws (0.00 - 0.02%) for drivers under 21. However, you can be charged with impaired driving at any BAC if an officer determines you are impaired.
How long does it take to sober up?
Your body eliminates alcohol at roughly 0.015% BAC per hour, regardless of your weight or gender. This means one standard drink (14g alcohol) typically takes 1 to 1.5 hours to metabolize. Nothing speeds this up significantly - coffee, cold showers, and food do not accelerate alcohol metabolism. The only remedy is time.
Need a Simpler Tool?
Our Alcohol Calculator provides a quick BAC estimate with fewer inputs - great for a fast check. This BAC Calculator is designed for users who want a detailed drink database, projected BAC curve over time, and state-level legal limit references.