Regardless of your field of practice, if you’re a lawyer you can bet the house you will be asked about DWI; What do i do if I am pulled over and have been drinking? How many drinks does it take to get drunk? Below, provides an explanation of how many drinks it may take to become intoxicated under the law. 

How is intoxication defined?

Most states define intoxication as having lost the normal use of one’s mental and/or physical faculties or having a blood alcohol level 0.08 or higher at the time of driving.

Calculating your blood alcohol content (BAC)

For an old school way of calculating your blood alcohol level, keep reading. For the new school way of doing it, you can type “blood alcohol calculator”into Google and find a number of online calculators.

Widmark Formula – the OG of Blood Alcohol Calculations

The most widely known formula for calculating blood alcohol content is the Widmark formula, named for Swedish Scientist, Erik M.P. Widmark (1889-1954) who was considered a pioneer in forensic toxicology.

The Widmark formulafocuses on how alcohol behaves in the body from the time it is consumed to the time it is eliminated.

Widmark Formula

Blood Alcohol Content = [alcohol consumed in grams / (body weight in grams x r)] x 100

(“r” refers to the distribution of water in the bodyand is a constant number of 0.55 for females and 0.68 for males)

A standard drink = one 12 oz beer, one 5 oz glass of wine, or one 1 ½ oz shot of liquor.

A standard drink is 14 grams.

Beginning the calculation of your blood alcohol level:

1) Alcohol consumed in grams (i.e. how much have you had to drink):

• Standard drinks consumed x 14 = alcohol consumed in grams.

2) Body weight in grams:

• Body weight in pounds x 454 = body weight in grams

3) Body weight in grams x “r”

• Body weight in grams x (0.55 for females or 0.68 for males)

4) Blood Alcohol Content (BAC)

• Plug in the numbers and multiply by 100 = Blood Alcohol Content

5) How long have you been drinking?

• Blood Alcohol Content – (Number of hours since drinking started x 0.015) = Approximate Blood Alcohol Content

0.015 refers our the rate our bodies metabolize alcohol per every hour.

This formula and any other online blood alcohol content calculator is an approximation at best. Because two people are not alike, there are many factors that impact the way a person’s body metabolizes alcohol. Also, Blood alcohol concentration is a percentage of ethanol/alcohol in the blood. For example a 0.08 means there are 0.08 grams of alcohol for every 100 mL of blood.

See below a chart that approximates your blood alcohol level based on number of drinks, number of hours spent drinking and body weight.

In calculating your blood alcohol level over a period of time you would subtract 0.015 for every hour spent drinking. For example, if you were a 200 lb. male who had 8 drinks you would find 0.15 on the chart above. If you had those 8 drinks over 3 hours you would subtract 0.045 (0.015 * 3 hours) from 0.15. Thus, your approximate BAC would be 0.10 (o.15 – 0.045).