Blood Alcohol Content (BAC) Calculator
Your Estimated BAC
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About Your Results
This is an estimate of your blood alcohol content. This calculation is for informational purposes only.
This calculator is not a legal tool and cannot replace a breathalyzer. Individual BAC levels vary based on food, medication, and metabolism. Do not drive if you have been drinking.
What is Blood Alcohol Content (BAC)?
Blood Alcohol Content (BAC), or Blood Alcohol Concentration, is a measurement of the percentage of alcohol (ethyl alcohol or ethanol) in a person's bloodstream. A BAC of 0.10% means that one part of alcohol is present for every 1,000 parts of blood in the body.
BAC is the standard metric used by law enforcement to determine legal impairment. Your BAC is affected by numerous factors, including your gender, weight, the number of drinks consumed, and the time frame over which they were consumed. It is also influenced by your metabolism, what you've eaten, and any medications you may be taking.
How This BAC Calculator Works
This calculator estimates your BAC using the widely recognized Widmark Formula. This formula is a standard method for estimating BAC based on key biological and consumption factors.
The Widmark Formula
BAC = ( (Total Alcohol in grams) / (Body Weight in grams * 'r') ) * 100 - (Hours * 0.015)
Where:
• Total Alcohol: We assume one "Standard Drink" contains 14 grams of pure alcohol.
• Body Weight: Your weight converted to grams.
• 'r' (Widmark Factor): The water distribution ratio.
• For Males: 0.68
• For Females: 0.55 (Females have a lower water-to-fat ratio, leading to a higher BAC from the same amount of alcohol).
• Hours: The time elapsed since the *first* drink.
• 0.015: The average rate at which the liver eliminates alcohol, lowering your BAC by 0.015% per hour.
What is a "Standard Drink"?
The accuracy of this calculator depends *entirely* on you correctly counting your drinks. A "standard drink" in the United States contains approximately 14 grams of pure alcohol. This is equivalent to:
- 12 oz (355 ml) of regular beer (at 5% ABV)
- 5 oz (148 ml) of wine (at 12% ABV)
- 1.5 oz (44 ml) of distilled spirits or hard liquor (at 40% ABV or 80 proof)
Be careful: Many modern craft beers, large wine pours, or mixed drinks contain more than one "standard drink."
BAC Levels and Stages of Impairment
Even small amounts of alcohol affect your judgment, coordination, and reaction time. The legal limit in most of the United States is 0.08%, but impairment begins long before that.
| Estimated BAC (%) | Common Effects |
|---|---|
| 0.02% - 0.03% | Slightly light-headed, relaxation, some loss of judgment. |
| 0.05% - 0.06% | Lowered inhibitions, reduced coordination and alertness. |
| 0.08% - 0.10% | (Legal Limit) Slurred speech, poor coordination, slowed reaction time. |
| 0.15% - 0.20% | Significant loss of balance, nausea, "blackout" potential. |
| 0.30% + | Loss of consciousness, risk of alcohol poisoning, potential death. |
BAC Calculator FAQs
This calculator provides a scientific estimate, not a legally precise reading. Real-world BAC is affected by many variables not included here, such as your individual metabolism, whether you've eaten (food slows alcohol absorption), medication, and body fat percentage. Use this tool for educational purposes only. It cannot replace a breathalyzer.
Your liver eliminates alcohol at a relatively fixed rate of about 0.015% per hour. This calculator estimates your "time until sober" by dividing your estimated BAC by 0.015. For example, if your BAC is 0.08%, it will take approximately 5 hours and 20 minutes to return to 0.00%.
No. Nothing can speed up the rate at which your liver metabolizes alcohol. Common myths like drinking coffee, taking a cold shower, or "walking it off" do not work. These actions might make you feel more *alert*, but they do not lower your BAC or reduce your impairment. Only time can make you sober.
This is due to physiological differences in body composition. On average, females have a higher percentage of body fat and a lower percentage of body water than males of the same weight. Since alcohol is water-soluble, it becomes more concentrated in the body's water. Less water to dilute the alcohol results in a higher BAC. This is accounted for in the Widmark formula by the 'r' factor (0.55 for females vs. 0.68 for males).