BAC Calculator
Blood Alcohol Content Estimator — Based on the Widmark Formula
Estimate Your BAC
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Understanding Blood Alcohol Content
Blood Alcohol Content (BAC) is a measurement of the amount of alcohol present in your bloodstream. It is expressed as a percentage of alcohol per volume of blood. For example, a BAC of 0.08% means 0.08 grams of alcohol per 100 milliliters of blood.
How Alcohol Is Absorbed
When you drink alcohol, it is absorbed into the bloodstream through the stomach lining and small intestine. Absorption typically begins within 5-10 minutes and peaks between 30-90 minutes after consumption, depending on several factors:
- Empty stomach: Alcohol absorbs faster without food
- Carbonation: Carbonated drinks may speed absorption
- Drink strength: Higher concentration means faster absorption
- Rate of consumption: Drinking quickly raises BAC faster
How Alcohol Is Eliminated
Your liver metabolizes alcohol at a relatively constant rate of approximately 0.015% BAC per hour (though this varies between 0.010-0.020%). This means:
- You cannot speed up sobriety with coffee, cold showers, or exercise
- Only time reduces your BAC
- About 90-98% of alcohol is metabolized by the liver; the rest is excreted through breath, urine, and sweat
Factors Affecting Your BAC
- Body weight: Heavier individuals generally have lower BAC at the same consumption level
- Biological sex: Women typically have higher BAC than men at the same weight and consumption, due to lower body water content and higher body fat percentage
- Food in stomach: Eating before or while drinking slows absorption
- Medications: Many medications interact with alcohol and can amplify effects
- Tolerance: Regular drinkers may feel less impaired at a given BAC, but their BAC is still the same and the physiological effects persist
- Genetics: Enzyme variations affect how quickly alcohol is metabolized
- Age: Older adults may feel effects at lower BAC levels
The Widmark Formula
This calculator uses the Widmark formula, developed by Swedish scientist Erik M.P. Widmark in 1932. It remains the most widely used method for estimating BAC:
BAC = (A × 100) / (W × r) − (β × t)
- A = grams of pure alcohol consumed (standard drinks × 14g)
- W = body weight in grams
- r = Widmark factor (0.68 for males, 0.55 for females)
- β = elimination rate (0.015% per hour average)
- t = total time in hours
BAC Impairment Levels
Alcohol affects the brain progressively as BAC increases. Below are typical effects at each level, though individual responses vary significantly.
Normal behavior. Little or no measurable impact on most individuals. Slight mood elevation may occur.
- Cognitive: Normal function
- Motor: Normal coordination
Mild relaxation, slight warmth, mood elevation. Subtle reduction in judgment and inhibition.
- Cognitive: Slight impairment in multitasking
- Motor: Minimal decline in tracking and fine motor skills
Noticeable euphoria, talkativeness, lowered alertness. Behavior may become exaggerated.
- Cognitive: Impaired judgment, reasoning, and memory
- Motor: Reduced coordination, slower reaction time
Clear deterioration in reaction time, hearing, vision, and judgment. At 0.08%, you are legally impaired in all US states.
- Cognitive: Poor judgment, impaired self-control, difficulty concentrating
- Motor: Impaired balance, speech, hearing, reaction time
Slurred speech, poor coordination, slowed thinking. Significantly impaired driving ability and risk of injury.
- Cognitive: Substantial impairment in perception, memory, and comprehension
- Motor: Staggering gait, major loss of balance and coordination
Major loss of balance and muscle control. Vomiting likely. Risk of choking, blacking out, and injury greatly increased.
- Cognitive: Severely impaired, possible blackout, confusion
- Motor: Gross impairment, inability to walk without assistance
Loss of consciousness likely. Risk of respiratory failure, aspiration, coma, and death. THIS IS A MEDICAL EMERGENCY.
- Cognitive: Possible unconsciousness, amnesia
- Motor: Bladder function lost, breathing may slow or stop
Legal Limits Around the World
Standard Drink Sizes
In the United States, a standard drink contains approximately 14 grams (0.6 ounces) of pure alcohol. Understanding what constitutes a standard drink is critical for accurate BAC estimation.
Regular Beer
One standard 12 oz can or bottle. Note that many craft beers are 7-12% ABV, meaning a single can could equal 1.5-2.5 standard drinks.
Table Wine
A standard pour is 5 oz, but typical restaurant and home pours are often 6-8 oz. A standard 750 mL wine bottle contains about 5 standard drinks.
Distilled Spirits
One standard shot. Mixed cocktails often contain 1.5-3 oz of spirits. A Long Island Iced Tea can contain 4+ standard drinks.
Common Misconceptions
- "Beer is safer than hard liquor" — False. A standard serving of beer, wine, or spirits all contain the same amount of pure alcohol (14g).
- "I only had a few drinks" — Mixed drinks, large pours, and high-ABV beverages can mean you consumed far more standard drinks than you counted.
- "Craft beer is just like regular beer" — Many craft beers are 8-12% ABV, meaning a single pint equals 1.5-2.5 standard drinks.
- "Wine is moderate drinking" — A typical restaurant wine pour (8 oz) is 1.6 standard drinks, not one.
Alcohol & Health
Short-Term Risks
Injury & Accidents
- Motor vehicle crashes (leading cause of alcohol-related death)
- Falls, burns, and drowning
- Impaired judgment leading to risky behaviors
Acute Health Effects
- Alcohol poisoning (can be fatal)
- Dehydration and electrolyte imbalance
- Impaired immune response
- Interactions with medications
Long-Term Health Effects
- Liver disease: Fatty liver, alcoholic hepatitis, cirrhosis
- Cardiovascular: High blood pressure, cardiomyopathy, arrhythmias, stroke
- Cancer: Increased risk of mouth, throat, esophagus, liver, colon, and breast cancer
- Neurological: Brain damage, dementia, peripheral neuropathy
- Mental health: Depression, anxiety, alcohol use disorder
- Digestive: Gastritis, pancreatitis, malnutrition
Guidelines for Moderate Drinking
Women
No more than 1 drink per day
No more than 7 drinks per week
Men
No more than 2 drinks per day
No more than 14 drinks per week
Source: NIAAA / Dietary Guidelines for Americans. Note: The 2025 Dietary Guidelines Advisory Committee recommends limiting intake further.
When to Seek Help
Consider seeking help if you:
- Drink more or longer than you intended
- Have tried to cut down but could not
- Spend a lot of time drinking or recovering from drinking
- Experience cravings or strong urges to drink
- Find that drinking interferes with work, school, or family
- Continue to drink despite problems it causes
- Need more alcohol to get the same effect (tolerance)
- Experience withdrawal symptoms when not drinking
SAMHSA National Helpline: 1-800-662-4357 (free, confidential, 24/7)
Find Treatment: findtreatment.gov
Frequently Asked Questions
Blood Alcohol Content (BAC) is a measurement of the concentration of alcohol in your bloodstream, expressed as a percentage. A BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood. BAC can be measured directly through a blood test, or estimated through breath testing (breathalyzer), urine testing, or mathematical formulas like the Widmark equation used here. Breath testing is most common for law enforcement, as it provides immediate results that correlate closely with blood levels.
This calculator provides a rough estimate only based on the Widmark formula. While the Widmark formula is scientifically validated and widely used in forensic toxicology, real-world BAC varies based on many factors this calculator cannot account for, including food consumption, individual metabolism, genetics, hydration level, medications, and health conditions. Your actual BAC could be significantly higher or lower than the estimate. Never use this calculator to decide whether you are safe to drive.
The Widmark formula accounts for weight, biological sex, amount consumed, and time. It does not account for:
- Whether you ate food before or while drinking
- Your individual metabolism rate (which varies widely)
- Medications that interact with alcohol
- Health conditions affecting liver function
- Body composition (muscle vs. fat ratio)
- Hydration level
- Rate of consumption during the drinking period
- Genetic factors (e.g., ALDH2 deficiency common in East Asian populations)
In the United States, the legal BAC limit for operating a motor vehicle is 0.08% in all 50 states, Washington D.C., and Puerto Rico. However, you can be arrested for impaired driving at any BAC level if an officer determines you are impaired. For drivers under 21, most states have a zero-tolerance law (0.00-0.02%). For commercial drivers, the limit is 0.04%. Many countries have lower limits (0.05% or even 0.00%). Even at BAC levels below 0.08%, your driving ability is impaired.
Your body eliminates alcohol at a relatively fixed rate of approximately 0.015% BAC per hour. This means if your BAC is 0.08%, it would take roughly 5-6 hours to reach 0.00%. However, individual elimination rates range from 0.010% to 0.020% per hour. Nothing speeds up this process — not coffee, cold showers, exercise, or fresh air. Only time eliminates alcohol from your system. This calculator provides an estimated time to sobriety, but your actual time may differ.
Call 911 immediately if you observe any of these signs of alcohol overdose (alcohol poisoning):
- Person is unconscious or cannot be awakened
- Slow or irregular breathing (fewer than 8 breaths per minute, or gaps of 10+ seconds)
- Vomiting while unconscious
- Seizures
- Blue-tinged or pale skin, especially lips or fingertips
- Hypothermia (low body temperature), cold or clammy skin
Do not leave the person alone. Turn them on their side to prevent choking if they vomit. Alcohol poisoning is a medical emergency that can result in permanent brain damage or death.
Important Disclaimer
This BAC calculator is for EDUCATIONAL and INFORMATIONAL purposes only.
- NEVER use this calculator to determine whether you are safe to drive, operate machinery, or perform any activity requiring attention and coordination.
- This is a mathematical estimate. Your actual BAC may be significantly higher or lower.
- Impairment begins with the first drink, even at very low BAC levels.
- The only way to ensure a BAC of 0.00% is to not drink at all.
- If you have been drinking, use a designated driver, rideshare, taxi, or public transportation.
This tool does not constitute medical, legal, or professional advice. Always consult qualified professionals for medical, legal, or substance use concerns.
Need Help? SAMHSA National Helpline: 1-800-662-4357 (free, confidential, 24/7) | In Crisis: Call 988 or 911
References & Sources
- Widmark EMP. Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung. Berlin: Urban & Schwarzenberg; 1932.
- National Institute on Alcohol Abuse and Alcoholism (NIAAA). What Is a Standard Drink? niaaa.nih.gov
- National Highway Traffic Safety Administration (NHTSA). Alcohol-Impaired Driving. nhtsa.gov
- Centers for Disease Control and Prevention (CDC). Alcohol and Public Health. cdc.gov
Last Updated: February 2026