Blood Alcohol Calculator
Estimate BAC based on drinks, weight, and time
Estimate your blood alcohol content based on body weight, sex, number of drinks, and time elapsed. This calculator uses the Widmark formula — but remember, it provides rough estimates only and should NEVER be used to decide whether to drive.
Most common answer: A 170-pound male who has consumed 3 standard drinks over 2 hours has an estimated BAC of about 0.053%. The legal limit in most US states is 0.08%.
This calculator provides rough estimates only and should NEVER be used to determine if you are safe to drive. BAC is affected by many factors not accounted for here including medications, food intake, health conditions, and individual metabolism. If you have consumed any alcohol, do not drive. Use a rideshare, taxi, or designated driver.
Affects metabolism rate (Widmark factor)
Relaxation, slight mood changes
Lowered inhibition, slight euphoria
Reduced coordination, impaired judgment
Poor muscle control, blurred vision, vomiting
Loss of balance, potential blackout
Loss of consciousness, risk of death
Each contains approximately 14 grams of pure alcohol.
This is an ESTIMATE only. Do NOT use this to decide whether to drive. If you have consumed any alcohol, arrange a safe ride home.
Blood Alcohol Calculator (BAC)
How to Use This Calculator
Enter your body weight, biological sex, number of standard drinks consumed, and hours since your first drink. The calculator estimates your current BAC using the Widmark formula.
IMPORTANT SAFETY WARNING
This calculator provides rough estimates only. Actual BAC depends on many factors including food intake, medications, health conditions, individual metabolism, and drink strength. If you have consumed any alcohol, do NOT drive.
The Widmark Formula
BAC = (Alcohol grams ÷ (Body weight grams × Widmark factor)) × 100 − (0.015 × hours)
One standard drink contains 14 grams of alcohol. Widmark factor: 0.68 for males, 0.55 for females.
BAC Levels and Effects
| BAC Level | Typical Effects |
|---|---|
| 0.02–0.03% | Slight relaxation, mild mood elevation |
| 0.04–0.06% | Lowered inhibitions, minor impairment |
| 0.07–0.09% | Impaired balance, speech, reaction time |
| 0.10–0.15% | Significant motor impairment, blurred vision |
| 0.16–0.30% | Severe impairment, potential blackout |
| 0.31%+ | Life-threatening — risk of death |
Sources
- Widmark, E.M.P. (1932). Principles and Applications of Medicolegal Alcohol Determination.
- NIAAA — What Is a Standard Drink?
- NHTSA — BAC and impairment effects
Disclaimer: This calculator is for educational purposes ONLY. It should NEVER be used to determine if you are safe to drive. If you need help with alcohol use, call SAMHSA: 1-800-662-4357.
Related Calculators
- Calorie Calculator — Know calories in drinks
- BMI Calculator — Check body mass index
- Water Intake Calculator — Stay hydrated
よくある質問
BAC (Blood Alcohol Content) is the percentage of alcohol in your bloodstream by weight. A BAC of 0.08% means 0.08 grams of alcohol per 100 milliliters of blood. This is the legal limit for driving in all US states for adults 21+. BAC is affected by weight, gender, number of drinks, time elapsed, food intake, and individual metabolism.
The body metabolizes alcohol at a fairly constant rate of about 0.015% BAC per hour, regardless of body size. This equals roughly one standard drink per hour. A BAC of 0.08% takes about 5.3 hours to reach 0.00%. A BAC of 0.15% takes about 10 hours. Nothing speeds this up. Coffee, food, water, and cold showers do not reduce BAC.
One standard drink contains 14 grams (0.6 oz) of pure alcohol. This equals: 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV / 80 proof). Many cocktails, craft beers, and wine pours exceed one standard drink. A 16-oz craft IPA at 7% is nearly 1.5 standard drinks.
Women typically have a higher BAC than men after drinking the same amount due to: lower body water content (55% vs 68%), resulting in less dilution of alcohol; generally lower body weight; lower levels of alcohol dehydrogenase (the enzyme that breaks down alcohol in the stomach); and hormonal differences that can affect metabolism.
Yes, eating before and while drinking slows alcohol absorption significantly. Food in the stomach delays gastric emptying, reducing the rate at which alcohol reaches the small intestine (where most absorption occurs). Eating can lower peak BAC by 10-30%. Protein and fat-rich foods have the greatest effect. However, food does not prevent impairment.
In all US states, the legal BAC limit is 0.08% for adults 21 and older. For commercial drivers, the limit is 0.04%. For drivers under 21, most states have zero tolerance laws (0.00% or 0.02%). Many countries have lower limits: 0.05% in most of Europe and Australia, 0.03% in Japan, and 0.00% in several countries. Even below 0.08%, you can be charged with impaired driving.
BAC calculators using the Widmark formula provide rough estimates only, typically within 0.01-0.02% of actual BAC. Many factors are not accounted for: food intake, medications, liver health, genetics, drink strength, and rate of consumption. These calculators should NEVER be used to determine if it is safe to drive. The only safe BAC for driving is 0.00%.
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