Who is Widmark and What is his Equation?

Who is Widmark and What is his Equation?

Erik Widmark was a Swedish researcher and a pioneer in researching ethanol (or alcohol) in the body. His work has been and remains very influential in forensic alcohol analysis.

Widmark researched how ethanol behaves in the body. He studied how after consumption, ethanol is absorbed, distributed, and eliminated. His work helped to show the level of alcohol in the body from consumption to elimination based on certain factors.

Widmark's Formula

Widmark's formula states that one’s blood alcohol content (BAC) is equal to the number of ounces of alcohol consumed, multiplied by a constant — for men by 3.75 and for women by 4.7 — and then divided by that person’s weight. In order to determine BAC at different time intervals, he chose a constant rate of elimination "B" (.017%) and time "T".

Here’s a visual depiction of the formula:

(ounces of alcohol) x (men 3.75, women 4.7) ­ B (elimination rate .017%) T (time/hours)

Example 1: A 130 pound woman downs 3 tequila shots.

What would her maximum BAC be, assuming all the alcohol was absorbed?

3 x 4.7 = 14.1

14.1 / 130 = .10 BAC

Example 2: A 210 pound man downs a 6 pack of beer.

What would his maximum BAC be, assuming all the alcohol was absorbed?

6 x 3.75 = 22.5

22.5 / 210 = .10 BAC

How Fast Does Your Blood Alcohol Level Start to Go Down?

Widmark’s formula can be employed to determine the BAC after passage of certain amount of time by utilizing the B and T factors of his equation.

According to Widmark’s formula, in the above two examples, both are over the .08 limit. If each waits about an hour and a half, the alcohol in their system would be eliminated by approximately .02 per hour, or .03 in about 90 minutes, and the BAC of each should drop below .08.

.10 ­- B (.017%) T (1.5) ⇒ .10 ­- .0255 ⇒ .07 BAC (after 90 minutes)

So, Widmark’s formula is a way to determine a person’s blood alcohol level at different time intervals once we learn their gender, weight, and their drinking pattern. 

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