Redfern Health Center

Blood Alcohol Concentration (BAC)

What is BAC?

BAC refers to the percent of alcohol in a person’s blood stream. A BAC of .10 percent means that an individual’s blood supply contains one part alcohol for every 1,000 parts blood.

In South Carolina, a person is legally intoxicated if he/she has a BAC of .08 percent or above.

Factors that determine BAC
  • Number of standard drinks (see below)
  • Amount of time in which drinks are consumed
  • Body weight
  • Gender
  • Food (to a much lesser extent)
One standard drink = 1/2 ounce of ethyl alcohol
  • One 12 oz. regular beer (4.5 percent alcohol) = .54 oz.
  • One 7 oz. malt liquor (7 percent alcohol) = .49 oz.
  • One 4.5 oz. glass of wine (12 percent alcohol) = .54 oz.
  • One jigger (1.25 oz.) of 80-proof liquor (40 percent alcohol) = .50 oz.
  • One-third jigger (.5 oz.) of Everclear (95 percent alcohol) = .48 oz.
More than one standard drink > 1/2 ounce
  • One 16 oz. cup of beer = .72 oz. = 1.4 drinks
  • One 40 oz. beer = 1.8 oz. = 3.6 drinks
  • One 22 oz. malt liquor = 1.5 oz. = 3 drinks
  • One 12 oz. glass of wine = 1.4 oz. = 2.9 drinks
  • One 12 oz. margarita = 2-4 drinks, depending on ingredients
  • One 12 oz. cup of trashcan punch = 4-10 drinks, depending on ingredients
Estimated and Approximate BAC for Men*

Male BAC

Estimated and Approximate BAC for Women*

BAC Female

BAC Effects

Even small amounts of alcohol in the system affect judgment and coordination. Increased amounts affect the body and mind more dramatically. Large amounts can kill.

The following approximate effects of different levels of blood alcohol concentration (BAC) are estimates only. Individual reactions vary, sometimes widely.

  • BAC .02 percent to .04 percent
    You may feel mildly relaxed and maybe a little lightheaded. Your inhibitions are slightly loosened, and whatever mood you were in before you started drinking may be mildly intensified.
  • BAC .05 percent to .07 percent
    You may feel warm and relaxed. If you’re the shy type when you’re sober, you would become more outgoing. Your behavior may become exaggerated, making you talk louder or faster or act bolder than usual. Emotions are intensified, so your good moods are better and your bad moods are worse. You may also feel a mild sense of euphoria.
  • BAC .08 percent to .09 percent
    You may believe you’re functioning better than you actually are. At this level, you may start to slur your speech. Your sense of balance is probably off, and your motor skills are starting to become impaired. Your ability to see and hear clearly is diminished. Your judgment is being affected, so it’s difficult for you to decide whether or not to continue drinking. Your ability to evaluate sexual situations is impaired. People may jokingly refer to this state of mind as “beer goggles,” but this blood alcohol concentration can have serious repercussions.
  • BAC .10 percent to .12 percent
    At this level you lack coordination and balance. Your motor skills are markedly impaired, as are your judgment and memory. You probably don’t remember how many drinks you’ve had. Emotions are exaggerated, and some people become loud, aggressive or belligerent. Men may have trouble getting an erection when their blood alcohol concentration is this high.
  • BAC .14 percent to .17 percent
    Your euphoric feelings may give way to unpleasant feelings. You have difficulty talking, walking or even standing up. Your judgment and perception are severely impaired. You may become more aggressive, and are at increased risk of accidentally injuring yourself or others. This is the point when you may experience a blackout.
  • BAC .20 percent
    You may feel confused, dazed or otherwise disoriented. You need help to stand up or walk. If you hurt yourself at this point, you probably won’t realize it because you won’t feel pain. Even if you are aware that you’ve injured yourself, you probably won’t do anything about it. At this point you may experience nausea and start vomiting. Your gag reflex is impaired, so you could choke if you throw up. Since blackouts are likely at this level, you may not remember any of this.
  • BAC .25 percent
    All mental, physical and sensory functions are severely impaired. You’re emotionally numb. There’s an increased risk of asphyxiation from choking on vomit and of seriously injuring yourself by falling or other accidents.
  • BAC .30 percent
    You’re probably in a stupor. You have little comprehension of where you are or what’s really going on around you. You may suddenly pass out and be difficult to awaken.
  • BAC .35 percent
    This blood alcohol concentration is similar to the physical effects of surgical anesthesia. You may stop breathing.
  • BAC .40 percent to .50 percent
    You are probably in a coma. The nerve centers controlling your heartbeat and respiration are slowing down, and it’s a miracle if you survive.
Scientists use the term “lethal dose” (LD) to describe the blood alcohol concentration that produces death from alcohol poisoning in half the population. Most authorities agree that BACs in the 0.40 percent to 0.50 percent range meet the requirement. Since studies of lethal dosage cannot be empirically tested in the laboratory, scientists estimate the LD for alcohol from post-mortem cases in which alcohol poisoning was the primary cause of death. Cases of fatal overdoses from alcohol at BACs lower than 0.40 percent have been documented, as have cases of survivors at BACs higher than 0.50 percent. To place this in perspective, a 100-pound woman or man who consumed nine to 10 standard drinks in less than one hour would be in the lethal dose range.