Understanding the science behind BAC calculations and the Widmark formula
Blood Alcohol Content (BAC) represents the percentage of alcohol in your bloodstream. A BAC of 0.08% means that 0.08% of your bloodstream is composed of alcohol. Understanding how BAC is calculated can help you make more informed decisions about drinking.
The most commonly used method for estimating BAC is the Widmark formula, developed by Swedish physician Erik Widmark in the 1930s. This formula takes into account several key factors that influence how your body processes alcohol.
Where 'r' is the distribution ratio: 0.68 for men and 0.55 for women
Larger individuals generally have more blood and body fluids, which dilutes the alcohol more than in smaller individuals. Additionally, muscle tissue contains more water than fat tissue, affecting alcohol distribution.
Women typically have a higher percentage of body fat and lower percentage of water in their bodies compared to men. This means alcohol is less diluted in women's bodies, leading to higher BAC levels from the same amount of alcohol.
Drinking quickly overwhelms your liver's ability to process alcohol. The liver can only metabolize about one standard drink per hour. Consuming alcohol faster than this rate causes BAC to rise rapidly.
Having food in your stomach slows the absorption of alcohol into your bloodstream. This doesn't prevent intoxication but can slow the rate at which your BAC rises.
Your liver is responsible for breaking down approximately 90-95% of the alcohol you consume. The process involves several steps:
This process occurs at a relatively fixed rate, which is why time is the only real way to sober up. Your body typically eliminates alcohol at a rate of 0.015% BAC per hour.
Now that you understand how BAC is calculated, try our free BAC calculator to estimate your blood alcohol content based on your drinks and body composition.