BAC calculator
Enter your weight, choose a drink, and add the number of servings and elapsed hours. This is an educational illustration, never a driving-safety assessment.
Your estimated BAC
A rough mathematical illustration based on your inputs, not a measurement of your blood alcohol level.
Method: simplified Widmark calculation using a uniform 90-minute absorption assumption and an illustrative elimination rate of 0.015 BAC percentage points per hour. The result is displayed to three decimal places for arithmetic clarity, not medical precision. Your real BAC may be higher or lower, and this cannot predict when you are safe to drive.
How to Use This BAC Calculator
This free BAC calculator gives a rough educational estimate of blood alcohol concentration (BAC). Enter your body weight in pounds, select a body-water assumption and a common drink, choose the number of servings, and enter how many hours have passed since drinking began. Then select Calculate BAC.
It is designed for common U.S. serving examples: a 12 fl oz regular beer (5% ABV), 12 fl oz light beer (4.2% ABV), 12 fl oz strong beer (7% ABV), 5 fl oz wine (12% ABV), or 1.5 fl oz liquor (40% ABV). Actual drinks can be larger or stronger, and a cocktail may contain several servings of liquor. Choose a preset only when it reasonably resembles what you drank.
What the BAC Estimate Means
Blood alcohol concentration is a measure of alcohol in the blood. This tool converts the selected drinks into estimated grams of pure alcohol and applies a simplified Widmark-based equation using body weight, a population-average distribution factor and elapsed time. It assumes the drinks started absorbing at the beginning of the entered time period, with absorption over about 90 minutes and a fixed example elimination rate. Those assumptions do not describe everyone's drinking pattern or physiology.
This result is not a BAC measurement. Food, medication, health, drink strength, pace of drinking and individual metabolism can change the outcome. BAC may continue rising after you stop drinking. Neither a low estimate nor 0.00% is evidence that it is safe or lawful to drive.
U.S. Standard Drinks
In the United States, one standard drink contains approximately 14 grams of pure alcohol. Common examples include 12 fl oz beer at 5% ABV, 5 fl oz wine at 12% ABV, and 1.5 fl oz distilled spirits at 40% ABV. Different products and pours may contain more or less alcohol than these examples.
Make a Safe Travel Plan
Never use an online BAC estimate to decide whether to drive. If you have consumed alcohol, arrange a sober driver, taxi, rideshare, or public transportation. Don't drink and drive.
BAC Calculator FAQs
Answers about the five inputs, standard drinks, the estimate and driving safety.
1. What is a BAC calculator?
It is an educational tool that estimates possible blood alcohol concentration using the information you enter. It cannot test or measure actual alcohol in your blood.
2. What information do I need to enter?
Only your body weight in pounds, a body-water assumption, one drink type, the number of servings, and hours since drinking began. You do not need exact drink dates or individual timestamps.
3. Why does this calculator ask for a body-water assumption?
A simplified Widmark equation uses a factor that approximates how alcohol distributes through body water. Male and female estimates are historical population averages, not exact measurements and not a reliable description of every person's body or gender.
4. Can I select beer, wine, or liquor?
Yes. Choose regular beer, light beer, strong beer, wine or liquor. Each preset uses a typical U.S. serving size and sample alcohol percentage. Check the label because actual drinks can vary.
5. What if I drank different kinds of alcohol?
This intentionally simple tool accepts one drink preset per calculation. Combining different drinks, larger pours or cocktails can make the estimate inaccurate; do not use the number for driving decisions.
6. What counts as a U.S. standard drink?
About 14 grams of pure alcohol. Typical examples are 12 fl oz beer at 5% ABV, 5 fl oz wine at 12% ABV, or 1.5 fl oz spirits at 40% ABV.
7. What does “hours since drinking began” mean?
Enter approximately how long ago your drinking session started. The model assumes the servings began absorbing then. It does not track later drinks individually, so the estimate can be very different from your actual BAC.
8. Is this BAC estimate accurate?
No online calculator can reliably tell you your actual BAC. The result depends on simplified assumptions and the accuracy of your entries; individual absorption and alcohol elimination vary considerably.
9. Can BAC continue rising after drinking stops?
Yes. Alcohol may continue to absorb after the last drink. The estimate cannot predict your actual peak BAC or when it will occur.
10. Can I drive if the calculator displays 0.00%?
No. An estimate of 0.00% does not prove sobriety, freedom from impairment, or that driving is lawful or safe. Never rely on this calculation to make a driving decision.
11. Does coffee, water, or a meal make me safe to drive?
No. Food can influence alcohol absorption, but coffee and water do not reliably clear alcohol from the bloodstream or reverse impairment. Plan sober transportation instead.
12. Does the calculator store my personal information?
No. Your entries are processed in your browser and are not submitted or saved by the calculator. The Reset button restores the starting values.