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Blood Alcohol Concentration

Blood alcohol concentration is the amount of alcohol in the blood, usually expressed as a percentage. The more alcohol per volume of blood (i.e., the higher your blood alcohol concentration) the more impaired you are.

  • An average drink (called a “standard drink”) will (usually) raise your blood alcohol concentration by approximately .02 percent. (See factors below that might influence your blood alcohol concentration).

  • Alcohol is metabolized by the body at the rate of approximately .015 percent per hour so one standard drink will (usually) be out of your body within 75 minutes (.02 – .015 = .005).

Factors that can affect your blood alcohol concentration include:

  • The amount of alcohol you drink. The more alcohol you drink the higher your BAC will rise.

  • The speed at which you drink alcohol. The faster you drink alcohol the faster your BAC will rise.

  • Your weight. The higher your weight the more water you will have in your body; this increases your overall blood volume. A higher blood volume has the effect of diluting the alcohol in the blood.

  • Your body fat and muscle mass. Muscle tissue absorbs alcohol whereas adipose (fat) tissue does not. When compared to a person of equal weight but with greater muscle mass, a person with a higher percentage of body fat will (usually) have a higher BAC.

  • Your gender. Females who drink the same amount as males, in the same amount of time, will (usually) have a higher BAC. This occurs because females are generally smaller than males, weigh less than males (i.e., lower overall blood volume), and have more body fat than males.

PLEASE NOTE: Females who drink alcohol while on birth control will tend to have a higher BAC than females of the same age, height and weight who drink alcohol and are not on birth control. This occurs because birth control changes biological processes (e.g., hormones, metabolism) and therefore affects how the liver processes alcohol in the body.

  • Drug use. Prescribed, over-the-counter, or illegal drugs will often interact with alcohol in the blood. This can lead to increased intoxication and sometimes very dangerous changes in the body’s physiology (i.e., changes in breathing rate, heart rate, attention, memory, and muscle coordination).

  • Food. The rate of alcohol absorption will be slower if you have food in your stomach—especially foods higher in protein; more food means slower alcohol absorption.

  • Carbonation. Alcoholic drinks that contain carbonation (e.g., Champaign or alcohol mixed with soda or seltzer) will increase the rate of alcohol absorption; more carbonation means a faster rise in BAC. This occurs because carbonation increases pressure in the stomach, which “pushes” alcohol into the bloodstream and “speeds up” gastric emptying (see Roberts & Robinson, 2007 in the reference section for more information).

  • Your mood. Changes in your mood (e.g., happy, sad, angry, stressed, anxious) have corresponding changes in biological processes (e.g., brain chemicals, hormones) which can affect how the body responds to, and processes, the alcohol in the body.

  • Time. Remember that TIME is the only way for alcohol to leave your body. It takes a little over 1-hour (approximately 70 – 75 minutes) for one alcohol drink to leave the body.

This external site is for informational purposes only. The information on this site is NOT LEGAL ADVICE. Your actual blood alcohol concentration depends on a variety of additional factors, like genetic makeup, personal health, and recent food consumption. These results are rough estimates for an average person only. Do not rely on these results to drive...

Never drink and drive!!!

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