How Our BAC Calculator Works
Our Blood Alcohol Content (BAC) calculator uses scientifically validated formulas to estimate your blood alcohol concentration based on multiple physiological and environmental factors. Understanding how it works can help you make more informed decisions about alcohol consumption.
Basic Information
We collect your weight and biological sex because these factors significantly affect how your body processes alcohol:
- Body Weight: Alcohol distributes throughout your body water. A heavier person has more body water to dilute the alcohol, resulting in a lower BAC for the same amount of alcohol consumed.
- Biological Sex: On average, female bodies have a higher percentage of body fat and lower percentage of water than male bodies of the same weight. This means alcohol is less diluted in females, typically resulting in higher BAC levels. We use scientifically established distribution ratios (0.68 for males, 0.55 for females).
- Drinking Start Time: This establishes the baseline for calculating alcohol absorption and elimination over time.
Drink Information
For each drink, we need to know:
- Drink Type & Volume: Different beverages contain different amounts of pure alcohol. A 12oz beer (5% ABV) contains roughly the same amount of alcohol as 5oz of wine (12% ABV) or 1.5oz of liquor (40% ABV) - each is considered one "standard drink."
- Alcohol Percentage (ABV): ABV stands for "Alcohol By Volume." A beer with 5% ABV means 5% of the liquid is pure alcohol. This allows us to calculate exactly how much alcohol you've consumed.
- Time Consumed: When you finished each drink matters because your body begins absorbing alcohol immediately and continues eliminating it at a constant rate (approximately 0.015% per hour for most people).
BAC Calculation
Our calculator uses the Widmark formula, enhanced with sigmoid absorption curves for accuracy:
BAC = (Alcohol consumed in grams / (Body weight in grams × r)) × 100
Where 'r' is the alcohol distribution ratio (0.68 for males, 0.55 for females)
The calculator then accounts for:
- Absorption Phase: Alcohol doesn't enter your bloodstream instantly. We model the absorption curve showing how BAC rises over 30-60 minutes after drinking.
- Elimination Phase: Your liver metabolizes alcohol at approximately 0.015% BAC per hour. This rate is relatively constant and can't be significantly accelerated.
- Multiple Drinks: When you have multiple drinks, each has its own absorption and elimination curve. The calculator sums these curves to show your total BAC over time.
Your Results
The results page shows you:
- Current BAC: Your estimated blood alcohol content right now
- Peak BAC: The highest your BAC reached (or will reach if still absorbing)
- Time to Sober: When your BAC is expected to return to 0.00%
- Time Below Legal Limit: When you'll drop below 0.08% (if applicable)
- Interactive Graph: Visual representation of your BAC over time