Blood Alcohol Content BAC Formula

BAC Calculator: Blood Alcohol Content (BAC) Formula

Long before digital technology came along to instantly compute a person’s concentration of alcohol within that drinker’s body, a Swedish scientist had run experiments and established a “BAC maths” calculator. Known for his work in finding a systematic way to estimate the absorption, distribution, and elimination of ethanol (alcohol) in the human body, he is credited with formulating his results in a mathematical equation.

By laboriously testing thousands of men and women, he was able to deduce a mathematical formula for estimating how much pure alcohol was needed to cause that person’s blood alcohol level to reach a certain level for each gender.


The “how drunk am I” calculator. In our modern world, knowing when you will be legally intoxicated to drive based on body weight, gender and height is highly valuable information. All DUI-DWI laws in America and other nations target certain “numbers” for which an illegal blood alcohol concentration will lead to criminal charges, and the need to hire lawyers near me to defend that case.

What is a Widmark Calculation?

With this formula for back calculation for breath alcohol or blood alcohol, a person imbibing an 80 proof liquor, 12 oz container, with a 6 hour start and ending time, could know an approximate alcohol blood level by employing the Widmark blood alcohol level calculator (BAC CALC). By retesting the same individual on 12 oz of beer, or 5 oz of 80 proof booze, Widmark isolated the factors that controlled the variables within the equation.

What does BAC Mean? The acronym “BAC” in the scientific world represents blood alcohol content or concentration. For decades, this Widmark formula on obtaining a BAC after hours of consuming alcoholic beverages was the gold standard worldwide.

The Widmark Equation. Erik M.P. Widmark became famous worldwide for this initial work in the late 1920s and early 1930s. He created the world’s first “calculate blood alcohol level” equation. Today, a rudimentary BAC level calculator can be bought for less than $50, but a forensic, law enforcement BAC alcohol calculator (with printer) can cost nearly $2000.

How to work out blood alcohol content. By being able to predict this BAC equation, the Swedish doctor enabled a person of a certain gender, height, weight, and body composition to obtain a ballpark estimation of how many drinks he or she can have and remain below the illegal BAC number. A police station near me will be using a breath alcohol testing device for drunk driving cases for which Dr. Widmark paved the way for such technology.


What does BAC stand for? If you were arrested for DUI and the police gave you a DUI breath test, they recorded your blood alcohol content or BAC. In all states, the maximum BAC level is 0.08% if you are over 21. The BAC level for drivers near me under 21 can be as low as 0.00%, which means zero tolerance.


Read more about Dr. Widmark in this bio written by Dr. A. W. Jones, of Sweden.


Widmark’s Blood Alcohol Calculator: BAC for Women and Men

Widmark’s basic BAC estimator alcohol formula for calculating a person’s estimated Blood Alcohol Content (BAC) at a particular time may be expressed as follows:

BAC Calculator Formula Widmark

% BAC = (A x 5.14 / W x r) – .015 x H

A = liquid ounces of pure alcohol consumed

W = a person’s weight in pounds

The r (rho) factor = a gender constant of alcohol distribution (0.73 for men and 0.66 for women), due to differences in the percentages of adipose tissue (body fat) for female subjects. The research indicated that women had higher fat content (on average) than men, due to the importance of bod fat when giving birth and nurturing babies.

H = hours elapsed since drinking commenced

The Numbers in the Widmark Formula Calculator

The 5.14 appearing in the formula is a conversion factor of .823 x 100/16, wherein .823 is used to convert liquid ounces to ounces of weight, 100 is used to convert the final figure to a percentage, and 16 is used to convert pounds to ounces. The .015 figure appearing in the formula is the average alcohol elimination rate for adults.

There are many online Blood Alcohol Content Calculators online. One of these is the American Addiction Centers You can use this for BAC for Women and BAC for men.


BAC Chart for Women


BAC Chart for Men


For more information on the gender constant of alcohol distribution, read our page about Blood Alcohol Content (BAC) Calculation & Distribution.


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