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Calculating BAC

There are times when you may want to calculate your blood alcohol concentration, such as before you leave a bar or restaurant, or if you have been arrested for Driving Under the Influence. When a cop stops you for DUI, he will ask you to perform one or more field sobriety tests, such as standing on one leg, following a light with only your eyes, or walking heel-to-toe in a straight line. If you fail any of these tests, and the officer suspects you may be under the influence of drugs or alcohol, they will ask you to submit to further testing, either a breath test or chemical (blood or urine) test.

What is Blood Alcohol Concentration?

Blood Alcohol Concentration (BAC) is the amount of alcohol in your blood. When you drink something alcoholic, the alcohol in your drink enters your bloodstream. The more you drink, the more alcohol there is in your blood. The legal limit for adults in most states, including Pennsylvania, is 0.08 percent. If your BAC is higher than 0.08 percent, you can be charged with driving under the influence (DUI). A BAC test measures the alcohol in your blood. A BAC of 0.08 means that there are 0.08 grams of alcohol for every 100 ml of blood.

For minors, a BAC of 0.02 percent or higher results in an automatic DUI charge, as Pennsylvania has a zero tolerance policy toward underage DUI.

What Factors Affect BAC?
  • Gender—Women almost always test a higher BAC than a man who had consumed the same number of drinks. This is largely because women tend to be smaller than men.
  • Body fat—A person with more body fat tends to test a higher BAC, because body fat does not absorb alcohol as easily.
  • Empty stomach—A person who has not eaten recently will have a higher BAC than someone who drank the same amount but who also ate a meal. This is because some of the alcohol is absorbed by the full stomach, and the BAC number is therefore lowered.
  • Body size—A smaller and lighter person will have a higher BAC than someone who is larger and heavier, because the larger person has more space for the alcohol to spread out in.
  • Determining BAC

It’s possible to make a rough estimate of your Blood Alcohol Content. The important thing to remember is that one drink equals: one 5-ounce glass of wine, a single 1.5-ounce shot of liquor, or one 12-ounce beer. The alcohol content in the wine is 15 to 20 percent, in the liquor, it’s 30 to 50 percent, and in the beer, it’s 4 to 4 ½ percent. A Long Island Iced Tea, which is a combination of five types of alcohol, is 22 percent alcohol.

To calculate your BAC, you need to know how many hours you spent drinking, the number of ounces of alcohol you consumed, the percentage of alcohol in the drinks, and your weight. There is a formula called Widmark’s Formula that will help you figure out your BAC.

BAC = (liquid ounces of alcohol consumed* x 5.14 / person’s weight in pounds x gender constant**) – .015 x hours elapsed since drinking began.

*ounces consumed times percentage of alcohol in the beverage

**The gender constant for alcohol distribution is .66 for women and .73 for men.

So, if you are a 150-pound adult woman who drank two 12-ounce beers in the last two hours …

% BAC = (1.20 x 5.14 / 150 x .66) - .015 x 2

% BAC = (6.168 / 99) - .03

% BAC = .062 - .03

% BAC = .032 (which is lower than the legal limit for adults of .08% and means you are not legally drunk)

Do this When Your BAC is too High

Remember that you are legally required to take the BAC test. If you refuse either a blood or breath test, your license will automatically be suspended, and you will receive an additional criminal charge. If you are arrested for DUI, call an experienced DUI attorney immediately.

If you have been charged with Driving Under the Influence, you require an experienced and knowledgeable DUI attorney to help you. The Logue Criminal Defense team has handled hundreds of DUI cases. Logue Law Group serves Pittsburgh, PA, West Virginia, and Ohio. Call us today for an initial consultation: 1-844-PITT-DUI or (412) 389-0805. Or, you may contact us online.

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