About BAC Calculator

Our Blood Alcohol Content (BAC) calculator helps you estimate your blood alcohol level based on the drinks you've consumed, your weight, and gender. The calculator uses the Widmark formula to provide accurate BAC estimations and shows you when you'll likely be sober.

Key Features: Real-time BAC monitoring, drink tracking with timestamps, BAC visualization over time, sobriety time estimation, support for both metric (kg, ml) and imperial (lbs, oz) units, and privacy-focused local storage.

Blood Alcohol Content (BAC) is a measurement of the amount of alcohol present in your bloodstream. It is expressed as a percentage, representing the weight of alcohol per volume of blood. For example, a BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood.

How BAC Affects You: Different BAC levels produce different effects. At 0.02-0.03%, you may feel relaxed with slightly impaired judgment. At 0.05-0.08%, coordination and reaction time are noticeably affected. At 0.08% and above (the legal limit in most jurisdictions), driving ability is significantly impaired. Higher levels can lead to severe intoxication, loss of consciousness, and even life-threatening alcohol poisoning.

Factors Affecting BAC: Your BAC is influenced by multiple factors including the amount and type of alcohol consumed, your body weight, gender (women typically have higher BAC than men after consuming the same amount), rate of consumption, food in your stomach, metabolism, and individual tolerance levels.

BAC Elimination: The human body metabolizes alcohol at a relatively constant rate of approximately 0.015-0.017% per hour. This means it takes time for your BAC to return to zero — you cannot speed up this process with coffee, cold showers, or exercise.

This calculator uses the Widmark formula, a widely-accepted scientific method for estimating blood alcohol content. The formula was developed by Swedish scientist Erik Widmark in the 1930s and remains the standard approach for BAC estimation.

The Formula: BAC = (Alcohol consumed in grams / (Body weight in grams × r)) - (Metabolism rate × Time). Where 'r' is the gender constant (0.68 for men, 0.55 for women), reflecting differences in body water content and alcohol distribution.

Calculation Steps:

1. Alcohol Consumed: We calculate the pure alcohol content by multiplying the drink volume by its alcohol percentage and the density of alcohol (0.789 g/ml).
2. Total Body Water: Your body weight is multiplied by the gender constant to estimate total body water where alcohol distributes.
3. Initial BAC: The total alcohol consumed is divided by your total body water to get the peak BAC.
4. Time-Based Reduction: BAC decreases at approximately 0.015% per hour as your liver metabolizes alcohol. We subtract this elimination rate based on time elapsed since each drink.

Important Limitations: This calculation provides an estimate based on average values. Individual results vary due to metabolism differences, food consumption, medications, liver health, hydration levels, and drinking patterns. The calculator cannot account for these personal factors, so actual BAC may differ from calculated values.

1. Enter your details: Input your weight and select your gender. The calculator supports both metric (kg) and imperial (lbs) units.
2. Add your drinks: Select from predefined drink types (beer, wine, spirits) or enter a custom drink with its volume and alcohol percentage.
3. View your BAC: Your estimated blood alcohol content updates in real-time as you add drinks.
4. Check the chart: The BAC over time chart shows how your BAC will change, including when you'll return to 0.00%.
5. See your sober time: The calculator estimates when your BAC will reach zero based on average metabolism rates.

We built BAC Calculator to promote responsible drinking and help people make informed decisions about alcohol consumption. Our goal is to provide a free, easy-to-use, and privacy-respecting tool that educates users about how alcohol affects their body.

All calculations happen directly in your browser. Your personal data (weight, gender, drinks) is stored only in your browser's local storage and is never sent to any server.