Blood Alcohol Calculator (BAC)
Blood Alcohol Content (BAC) estimates alcohol concentration in blood based on drinks consumed, weight, gender, and time elapsed. One standard drink = 12 oz beer (5%), 5 oz wine (12%), or 1.5 oz liquor (40%). Men metabolize ~0.015% per hour, women slightly slower. Legal limit: 0.08% in most US states. 0.02-0.05% = mild impairment, 0.08%+ = legally intoxicated, 0.30%+ = life-threatening.
Estimate your Blood Alcohol Content (BAC) using the Widmark formula. Enter gender, weight, drinks consumed, and time elapsed to get an estimated BAC level with impairment information and time until sober.
⚠️ Important Disclaimer
This calculator provides a rough estimate only. Actual BAC varies by individual based on metabolism, food intake, medications, health conditions, and other factors. Never drink and drive. This tool is not intended for legal, medical, or safety purposes. When in doubt, do not drive.
Biological Sex
Used for Widmark factor (0.73 male, 0.66 female)
Body Weight
Drinks Consumed
Hours Since First Drink
BAC Level Reference Chart
| BAC % | Level |
|---|---|
| 0.02% | Relaxation |
| 0.05% | Lowered Inhibition |
| 0.08% | Legal Limit (US) |
| 0.10% | Significant Impairment |
| 0.15% | Major Impairment |
| 0.30% | Severe Impairment |
| 0.40% | Life-Threatening |
Standard Drink Sizes
| Drink | Volume | ABV | Pure Alcohol |
|---|---|---|---|
| 🍺 Beer | 12 oz (355 ml) | 5% | 0.6 oz |
| 🍷 Wine | 5 oz (148 ml) | 12% | 0.6 oz |
| 🥃 Spirits | 1.5 oz (44 ml) | 40% | 0.6 oz |
| 🍸 Cocktail | ~4 oz (118 ml) | ~15% | ~0.6 oz |
Each standard drink contains approximately 0.6 oz (14g) of pure alcohol.
⚠️ Disclaimer
- • This calculator provides an estimate only using the Widmark formula.
- • Real BAC depends on food intake, metabolism, medications, hydration, liver function, and many other factors.
- • Never rely on this tool to determine if you are safe to drive.
- • This tool is not for legal, medical, or safety purposes.
- • If you have consumed alcohol, use a designated driver, rideshare, or taxi.
What is Blood Alcohol Content (BAC)?
Blood Alcohol Content (BAC), also known as Blood Alcohol Concentration or Blood Alcohol Level, is a measurement of the percentage of alcohol in a person's bloodstream. A BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood. BAC is the standard metric used by law enforcement and medical professionals to assess alcohol intoxication.
In the United States, a BAC of 0.08% is the legal limit for driving in all 50 states. However, impairment begins well before this level — even a BAC of 0.02% can affect visual function and the ability to multitask. Commercial drivers face a stricter limit of 0.04%, and for drivers under 21, most states enforce a zero-tolerance policy (0.00% or 0.02%).
How the Widmark Formula Works
This calculator uses the Widmark formula, developed by Swedish researcher Erik Widmark in the 1930s. The formula estimates BAC based on the amount of alcohol consumed, body weight, gender, and time elapsed:
- A = Total alcohol consumed in fluid ounces
- W = Body weight in pounds
- r = Gender constant (0.73 for males, 0.66 for females)
- H = Hours since first drink
- 5.14 = Conversion constant for fluid ounces to blood volume
- 0.015 = Average alcohol elimination rate per hour
The gender constant (“r” value, or Widmark factor) reflects average differences in body water content between biological males and females. Males typically have a higher body water ratio, which dilutes alcohol more effectively.
Factors That Affect BAC
🍔 Food Intake
Drinking on an empty stomach can result in a BAC up to 3 times higher than drinking after a full meal. Food slows absorption by keeping alcohol in the stomach longer.
💊 Medications
Many medications interact with alcohol, amplifying its effects. Antihistamines, painkillers, antidepressants, and other drugs can make alcohol more potent.
💧 Hydration & Health
Dehydration concentrates alcohol in the blood. Liver health, overall fitness, and chronic alcohol tolerance also significantly affect metabolism rates.
⏱️ Rate of Consumption
Drinking quickly overwhelms the liver's ability to metabolize alcohol (about one standard drink per hour), leading to rapid BAC increase.
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How to Use
- Enter your value in the input field
- Click the Calculate/Convert button
- Copy the result to your clipboard
Frequently Asked Questions
- What is BAC and how is it measured?
- BAC (Blood Alcohol Content) is the percentage of alcohol in your bloodstream. A BAC of 0.08% means 0.08 grams of alcohol per 100 milliliters of blood. It can be measured directly via blood tests, or estimated using breath analyzers (breathalyzers), urine tests, or mathematical formulas like the Widmark formula used in this calculator.
- What is the legal BAC limit for driving?
- In the United States, the legal BAC limit for drivers over 21 is 0.08% in all 50 states. Commercial drivers face a stricter limit of 0.04%. Most states have zero-tolerance laws for drivers under 21, with limits of 0.00% to 0.02%. Many other countries have lower limits — for example, 0.05% in Australia and most of Europe, and 0.03% in Japan and India.
- How long does it take for BAC to reach zero?
- The body metabolizes alcohol at an average rate of about 0.015% BAC per hour (roughly one standard drink per hour). So a BAC of 0.08% would take approximately 5.3 hours to reach 0.00%. However, this rate varies by individual — factors like liver health, genetics, food intake, and medications all affect how quickly you process alcohol. Nothing can speed up this process; coffee, cold showers, and exercise do not lower BAC faster.
- What is the Widmark formula for calculating BAC?
- The Widmark formula is: BAC = (A × 5.14 / (W × r)) − 0.015 × H, where A is total alcohol consumed in fluid ounces, W is body weight in pounds, r is the Widmark factor (0.73 for males, 0.66 for females), H is hours since first drink, and 0.015 is the average hourly metabolism rate. This formula provides an estimate — actual BAC can differ significantly based on individual factors.
- What is a standard drink?
- In the US, a standard drink contains approximately 0.6 ounces (14 grams) of pure alcohol. This is equivalent to: 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV). Many cocktails and craft beers contain more alcohol than a standard drink — an IPA at 7% ABV or a large pour of wine can equal 1.5 to 2+ standard drinks.
- Why does gender affect BAC?
- Biological sex affects BAC because of differences in body composition. Males typically have a higher percentage of body water (about 58%) compared to females (about 49%). Since alcohol distributes through body water, the same amount of alcohol results in a higher concentration (BAC) in someone with less body water. The Widmark factor accounts for this: 0.73 for males and 0.66 for females. Hormonal differences can also affect alcohol metabolism rates.
- Can I use this BAC calculator to determine if I am safe to drive?
- No. This calculator provides a rough mathematical estimate only and should NEVER be used to determine if you are safe to drive. Actual BAC varies significantly based on metabolism, food intake, medications, health conditions, tolerance, and many other individual factors that this formula cannot account for. If you have consumed any alcohol, the safest choice is always to use a designated driver, rideshare, taxi, or public transportation.