Blood Alcohol Content Calculator

Understanding Blood Alcohol Content (BAC)

Blood Alcohol Content (BAC) is the metric used by law enforcement and medical professionals to determine intoxication levels. It represents the percentage of alcohol in your bloodstream. A BAC of 0.10% means that one-tenth of a percent of your blood volume is alcohol. While this sounds small, it has profound chemical effects on the brain.
Disclaimer: This calculator is for educational estimates only. Metabolism varies widely. NEVER drink and drive. If you have been drinking, call a taxi or rideshare.

The Widmark Formula

This calculator relies on the Widmark Formula, the gold standard for BAC estimation since the 1930s. It considers four main variables:

1. Amount of Alcohol Consumed
Not all drinks are created equal. A "standard drink" in the US contains roughly 14 grams of pure alcohol.
- 12 oz beer (5% ABV)
- 5 oz wine (12% ABV)
- 1.5 oz distilled spirits (40% ABV / 80 proof)
If you drink a "pint" of craft IPA (16oz at 7%), that is nearly 2 standard drinks in one glass.

2. Body Weight
Alcohol is distributed through the water in your body. Heavier people generally have more body water, diluting the alcohol more than lighter people. A 200lb person will have a lower BAC than a 120lb person after drinking the same amount.

3. Gender (Body Composition)
Biological females typically have a higher body fat percentage and lower water content than biological males of the same weight. They also have less of the enzyme alcohol dehydrogenase. This means alcohol is more concentrated in the blood of females, resulting in a higher BAC for the same intake.

4. Time Elapsed
Your liver is the engine that removes alcohol. On average, the liver processes about 0.015% per hour. Time is the only thing that lowers BAC. Coffee, cold showers, and water do not speed up this process.

The "Stages" of Intoxication

0.02% - 0.03%: Relaxation
Slight mood elevation. Warm feeling. Driving ability usually not impaired yet.

0.05% - 0.06%: Impairment begins
Relaxation turns to minor impairment. Judgment is slightly reduced. Fine motor skills (like tracking a moving object) begin to decline.

0.08%: The Legal Limit
In all 50 US states, it is illegal to drive with a BAC of 0.08% or higher. Balance, speech, vision, and reaction time are noticeably impaired. Self-control is reduced.

0.10% - 0.15%: Intoxication
Significant impairment. Slurred speech. Unsteady gait. Aggression or overly emotional behavior is common. Vomiting may occur.

0.30%+: Danger Zone
Stupor or loss of consciousness. Risk of death due to respiratory arrest.

Why You Can't "Feel" Your BAC

Tolerance plays a huge role in how you feel, but tolerance does not change your BAC. A heavy drinker might "feel fine" at 0.10%, but their reaction times and legality to drive are just as impaired as a novice drinker at 0.10%. Do not trust your feelings.