Wisconsin Department of Transportation

Alert: The following services will be unavailable on Saturday, January 5, 2013 from 12 a.m. (midnight) to 6 a.m. CST due to system maintenance.

Blood/Breath Alcohol Concentration (BAC) calculator

Blood/Breath Alcohol Concentration (BAC) is the amount of alcohol in the bloodstream or on one's breath. BAC is expressed as the weight of ethanol, measured in grams, in 100 milliliters of blood, or 210 liters of breath. BAC can be measured by breath, blood, or urine tests.

  • Wisconsin defines legal intoxication for purposes of driving as having a BAC of 0.08 or greater, in most cases. But alcohol may affect driving skills at BACs of 0.05 or even lower.
  • Driving skills, especially judgment, are impaired in most people long before they show signs of drunkenness. The public usually associates BAC with "drunk driving." But it's more accurate to refer to "alcohol-impaired" driving because you do not have to be "drunk" to be impaired in your ability to safely drive a car.

Using the BAC calculator

Use this calculator to instantly compute your estimated blood/breath alcohol concentration.

  • Keep in mind the results generated are estimates.
  • The primary purpose is to provide information about the responsible use of alcohol.

Instructions: Please select weight, drinks consumed, time period and gender and click the "compute your BAC" button:

Weight: (pounds)
Drinks consumed: (12 oz. beer or equivalent)
Over time period: (hours)
Gender:  

Your BAC will be:

Disclaimer

Note: This BAC calculator is "JavaScript-based" and your browser will need JavaScript enabled to work. This calculator may not work with some older browsers that do not support JavaScript.

What can affect your BAC?

  • How much alcohol you drink.
  • How fast you drink. In general, the quicker you drink, the higher your peak BAC will be.
  • Body size. Large people tend to reach lower BACs than smaller people, given the same amount of alcohol.
  • Food in your stomach. When there is food in your stomach, alcohol is absorbed more slowly into the blood stream. The BAC rises more rapidly when you drink on an empty stomach, because there is no food in which to dilute the alcohol.
  • Type of mixer used. Water and fruit juices mixed with alcohol may slow the absorption process, while carbonated beverages may speed it up.
  • Gender differences.
    • Women reach higher BACs faster because they have less water in their bodies and more adipose tissue (fat), which is not easily penetrated by alcohol.
    • A man and a woman, with all other factors being equal, both drinking the same amount of alcohol, will have different BAC levels. Hers will be higher.

Disclaimer

Your actual BAC is dependent on many complex factors, including your emotional and physical condition and health, and what you've recently ingested (including food, water, medications and other drugs).

  • No blood/breath alcohol calculator is 100% accurate.
  • The best that can be done is a rough estimation of your BAC level.

You should not consider this to be a guideline for how much you can drink and still drive responsibly, or avoid being arrested! The best policy is don't drink and drive. Period.

NOTE: The basic formula for estimating a person's blood/breath alcohol concentration comes from the National Highway Traffic Safety Administration.

Questions about the content of this page:
Colette Brown, Colette.brown@dot.wi.gov
Last modified: January 15, 2014

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