Free BAC Calculator – Estimate Your Blood Alcohol Concentration Safely
Estimate your current Blood Alcohol Concentration (BAC) using the globally recognized Widmark Formula. By analyzing your weight, gender, the number of drinks you've consumed, and the time elapsed, this tool calculates your estimated intoxication level and your time until absolute sobriety.
How to Estimate Your BAC
Calculating your BAC accurately requires honesty regarding how much you have consumed and over what time period. Follow these four steps to generate an educational estimate of your current intoxication levels.
Input Biology
Select your biological gender and body weight. These variables determine the exact water distribution constant (r) used to calculate alcohol dispersion.
Add Drinks
Log the number of Standard Drinks you have consumed. Be extremely accurate—many craft beers and cocktails equal more than one standard drink.
Input Time
Enter the total number of hours that have passed since you took your very first sip of alcohol. Your liver requires time to begin clearance.
Review Estimate
View your estimated BAC and remaining time to absolute sobriety. Remember that this is a mathematical estimate and should never justify driving.
What is a "Standard Drink"?
The most common reason people accidentally exceed the legal limit is because they do not understand what constitutes a standard drink. In the United States, a standard drink contains exactly 14 grams (0.6 ounces) of pure ethanol.
A standard 12-ounce can or bottle of regular beer. Warning: Many modern craft IPAs range from 7% to 9% ABV, making a single pint equal to nearly two standard drinks.
A standard 5-ounce pour of wine. Most restaurant pours are generously larger than 5 ounces, meaning a single glass often constitutes 1.5 standard drinks.
A standard 1.5-ounce shot of 80-proof spirits (vodka, whiskey, gin, rum). Mixed cocktails often contain multiple shots, making them highly deceptive.
The Biology of Alcohol Clearance
Your liver is responsible for metabolizing roughly 90% to 95% of the alcohol you consume using the enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH).
Regardless of your height, weight, or biological gender, a healthy human liver can only metabolize alcohol at a strict, continuous rate of approximately 0.015% BAC per hour.
*Because the liver processes alcohol linearly, a BAC of 0.08% will universally take over 5 hours to drop to exactly 0.00%.
Debunking Sobering Up Myths
There is a dangerous amount of misinformation surrounding how to sober up quickly. Because the liver works at a fixed rate, it is biologically impossible to accelerate alcohol metabolism through physical actions or home remedies.
The Science: The Widmark Formula
Developed by Swedish scientist Erik M.P. Widmark in the 1930s, this equation remains the global gold standard for estimating blood alcohol levels in forensic and clinical settings:
BAC = [Alcohol consumed (g) / (Body Weight (g) × r)] × 100 − (0.015 × Hours)
- r (Distribution Constant): Widmark established that alcohol distributes primarily in body water. Because men average 68% body water and women average 55%, the constant is set at 0.73 for males and 0.66 for females.
- 0.015 (Elimination Rate): The standard metabolic elimination rate subtracted per hour.
Frequently Asked Questions
What is the Widmark Formula?
The Widmark Formula is the internationally recognized scientific equation for estimating Blood Alcohol Concentration (BAC). It calculates the ratio of pure alcohol consumed against your body weight, factoring in a gender-specific water distribution constant, and subtracts the alcohol your liver has metabolized over time.
What is considered a standard drink size?
In the United States, a standard drink contains roughly 14 grams (0.6 ounces) of pure alcohol. This is typically equal to one 12 oz regular beer (5% ABV), one 5 oz glass of wine (12% ABV), or one 1.5 oz shot of distilled spirits (40% ABV).
How long does it take for BAC to drop?
On average, a healthy human liver metabolizes and clears alcohol from the bloodstream at a steady rate of approximately 0.015% per hour. If your BAC is 0.06%, it will take roughly 4 hours for your BAC to drop to exactly 0.00%.
Does throwing up lower your BAC?
Throwing up will only remove unabsorbed alcohol that is still sitting in your stomach. It does absolutely nothing to lower the Blood Alcohol Concentration (BAC) of the alcohol that has already been absorbed into your bloodstream.
Does coffee or a cold shower sober you up?
No. Caffeine from coffee might make you feel more awake and alert, but neither coffee nor cold showers can speed up the enzymes in your liver that metabolize alcohol. Only time can lower your BAC and truly sober you up.
Does eating food prevent you from getting drunk?
Eating heavy, carb-rich foods before or during drinking does not prevent intoxication, but it significantly slows down the absorption of alcohol from your stomach into your bloodstream, preventing a rapid spike in your BAC.
Why do women generally have a higher BAC than men after the same amount of alcohol?
Women generally have a lower percentage of total body water than men of the exact same weight. Because alcohol is highly water-soluble, it becomes more concentrated in a woman's bloodstream. Women also naturally possess less of the stomach enzyme (ADH) that breaks down alcohol.
What factors affect blood alcohol concentration?
Your BAC is directly affected by the total amount of pure alcohol consumed, the time frame over which it was consumed, your biological gender, your total body weight, and whether you consumed food before drinking.
Is an online BAC calculator 100% accurate?
No online calculator can be 100% accurate. They provide mathematical estimates based on averages. They cannot account for your personal genetics, liver health, hydration levels, or exact stomach contents. Never use an online calculator to determine if you are safe to drive.
What is the legal driving limit?
In the United States and the UK, the federal legal driving limit is 0.08% BAC. However, many countries (and states for commercial drivers) have stricter limits of 0.05% or 0.02%. Impairment begins long before 0.08%, so the safest driving limit is always 0.00%.
Crucial Safety Disclaimer: This BAC Calculator is strictly an educational tool designed to provide mathematical estimates based on the Widmark Formula. It is NOT a substitute for a breathalyzer, blood test, or professional medical/legal advice. Your actual BAC may vary significantly due to genetics, food consumption, medications, and liver health. NEVER use this calculator to determine if it is safe to drive, operate machinery, or engage in dangerous activities. If you have been drinking alcohol, the only safe choice is zero driving.