Understanding Intoxication: The Blood Alcohol Content (BAC) Calculator

Disclaimer: This calculator provides an estimate for informational and educational purposes only. It is not a legal tool and should not be used to determine if it is safe to drive or operate machinery. Individual metabolic rates and other factors can cause significant variation. If you have been drinking, do not drive.

Blood Alcohol Content (BAC) is a measure of the percentage of alcohol in a person's bloodstream. A BAC of 0.10% means that one-tenth of one percent of a person's blood, by volume, is alcohol. It is the standard metric used by law enforcement and medical professionals to quantify the level of alcohol intoxication. As BAC increases, so does the level of impairment, affecting coordination, judgment, reaction time, and vision.

This calculator estimates your BAC based on the Widmark formula, a widely accepted scientific method. It takes into account the number of standard drinks consumed, your body weight, your gender, and the time elapsed since you started drinking. The formula accounts for the fact that alcohol is distributed in the water content of the body, which differs between genders, and that the body eliminates alcohol at a relatively constant rate. While this tool can provide a useful approximation of your BAC, it is crucial to understand that it is only an estimate. Your actual BAC can be influenced by many factors not included in this simple calculation, such as your metabolism, whether you've eaten recently, your body fat percentage, and any medications you may be taking.

The Widmark Formula Explained

The calculator uses a version of the Widmark formula to estimate BAC:

BAC % = [(Alcohol Consumed in grams / (Body Weight in grams × r)) × 100] - (Hours Since First Drink × 0.015)

Alcohol Consumed: This is calculated based on the number of 'standard drinks'. In the United States, one standard drink contains approximately 14 grams of pure alcohol. This is equivalent to one 12-ounce beer (5% ABV), one 5-ounce glass of wine (12% ABV), or one 1.5-ounce shot of distilled spirits (40% ABV).
Body Weight: Converted to grams for the formula.
Gender Constant (r): This is the water distribution ratio in the body. The average value is 0.68 for men and 0.55 for women. Women generally have a higher percentage of body fat and less body water than men of the same weight, which means alcohol becomes more concentrated in their bloodstream.
Elimination Rate: The formula subtracts an average alcohol elimination rate of 0.015% per hour. This accounts for the alcohol that your liver metabolizes over time.

General Effects of Alcohol at Different BAC Levels

BAC Level (%)	Typical Effects
0.02 - 0.03	Mild euphoria, slight relaxation. No significant loss of coordination.
0.04 - 0.06	Feeling of warmth and relaxation, minor impairment of reasoning and memory, lowering of caution.
0.07 - 0.09	Slight impairment of balance, speech, vision, reaction time, and hearing. Judgment and self-control are reduced. In the US, it is illegal to drive with a BAC of 0.08% or higher.
0.10 - 0.12	Significant impairment of motor coordination and loss of good judgment. Slurred speech, poor coordination, and slowed thinking.
0.13 - 0.15	Gross motor impairment and lack of physical control. Blurred vision, major loss of balance. Euphoria is reduced, and dysphoria (anxiety, restlessness) begins to appear.
0.16+	Dysphoria predominates. Nausea may appear. The drinker has the appearance of a "sloppy drunk." High risk of blackout.
0.25+	Severe intoxication. Needs assistance in walking; total mental confusion. High risk of accidental injury.
0.35+	Loss of consciousness. Risk of respiratory arrest and death.

Blood Alcohol Content (BAC)