What is BAC? Blood Alcohol Content Explained
What is Blood Alcohol Content?
Blood Alcohol Content (BAC) is the percentage of alcohol in your bloodstream by weight. A BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood. BAC is the standard measure used for legal and medical purposes to quantify alcohol intoxication.
The Widmark Equation
The most commonly used formula for estimating BAC is the Widmark equation, developed by Swedish physician Erik Widmark in the 1930s:
BAC = (A / (W ร r)) ร 100 โ (ฮฒ ร t)
- A = grams of pure alcohol consumed (1 standard drink = 14g)
- W = body weight in grams
- r = Widmark ratio (0.68 for males, 0.55 for females)
- ฮฒ = alcohol elimination rate (~0.015% per hour)
- t = time in hours since drinking began
Factors That Affect BAC
- Body weight: Larger people have more body water to dilute alcohol.
- Biological sex: Women generally have less body water and more body fat, leading to higher BAC from the same amount of alcohol.
- Food intake: Food in the stomach slows alcohol absorption, reducing peak BAC.
- Rate of consumption: Drinking faster produces higher peak BAC.
- Metabolism: Liver enzyme activity varies by individual and genetics.
- Medications: Many medications interact with alcohol and can amplify its effects.
BAC Levels and Effects
0.02โ0.03%Slight relaxation and mood elevation. Minimal impairment.
0.04โ0.06%Feeling of well-being. Lowered inhibitions. Minor impairment of reasoning.
0.07โ0.09%Impaired balance and speech. Reduced reaction time. Judgment clearly affected.
0.10โ0.15%Significant motor impairment. Slurred speech. Reduced coordination.
0.16โ0.29%Severe impairment. Disorientation. Nausea. Risk of blackout.
0.30%+Loss of consciousness. Alcohol poisoning. Life-threatening. Call 911.