How to Calculate Blood Alcohol Level

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Blood Alcohol Content, or BAC, is a measure of the ratio of alcohol in your blood. Follow these steps to learn how to calculate your BAC and know when it is legally safe to drive.


  1. Understand BAC. A BAC of .10 means 1 part alcohol for every 1,000 parts blood. Police use a breathalyzer to get your BAC but if you dont have a breathalyzer handy, youll have to do the math so that you can work out when you are safe to drive.
  2. Pick your poison. The first step in determining your BAC is knowing the alcohol content of your drink of choice. You also need to know what determines a standard drink.
    • Beer is usually 4%-6% alcohol. This varies, depending on the type of beer. Your best bet is to check the label.
    • One drink of wine is measured as 5 ounces. This includes white, red, rose, and champagne.
    • One drink of hard liquor is measured as 1.5 ounces, or one shot of liquor which typically contains 40% alcohol. Remember, some drinks are made with even stronger potency, like 151 proof rum or grain alcohol. Thus, your BAC will rise more quickly drinking hard liquor in place of beer or wine.
  3. Weigh your options. Calculating your BAC depends on your gender and your weight. Alcohol is absorbed differently by men and women. Mens bodies handle alcohol better. Men typically weigh more than women and so have the advantage in absorbing alcohol. For instance, a 180 pound man who has had four drinks in one hour will have a BAC of .08. In the same hour, his 120 pound female friend needs only two drinks to reach the same BAC of .08. Use the online BAC Calculator noted below under "Sources and Citations".
  4. Keep tabs on the time. Time will tell. As the night drags on and you consume drink after drink, the hours will have an effect on your BAC. As a general rule, subtract .015 from your total BAC for each hour that passes since your first drink. A 180-pound man whos had four drinks has a BAC of .08. If he waits stops drinking for one hour, his BAC may drop to .065, and hes legal to drive.
  5. Always keep in mind that there are many factors involved in a persons reaction to alcohol. Your BAC can be affected by the following BAC variables:
    • hereditary factors
    • medication
    • metabolism
    • hormonal factors; and
    • the amount of food in your stomach
  6. Always drink responsibly. Alcohol is just one part of a fulfilled life. Learn to pace your drinks and drink wisely; focus most on enjoying your time among friends. That way you can keep yourself, and anyone around you, safe and sound.


  • Drink responsibly and obey all local laws regarding age limits.

If you drive, there are items at low prices available in eBay as well as many other markets which can measure your BAC by testing your breath, and tell you when it it is legally acceptable for you to drive after using alcohol. They may save you thousands of dollars in lawyers fees, fines and increased insurance premiums, as well as save your life or the life of another person. Look for alcohol blood testers, Alcohol breathalysers etc. Drink smart, drive smart!


  • Be extra vigilant during the holiday season and on celebratory occasions.

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Sources and Citations

  • VideoJug Video demonstration of calculating blood alcohol level (BAC). Original source of article. Shared with permission and appreciation.

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