Number of Drinks and Blood Alcohol Content (BAC)

How Much Can You Drink Before You Are Affected?

Models pose as friends drinking
Your BAC determines your safe drinking limit. Morsa Images/Getty Images

Here is a general guide to estimating your Blood Alcohol Concentration (BAC), based on your body weight and speed of drinking:

One Drink

One American standard drink will, on average, produce a Blood Alcohol Concentration of about 0.02, and most light and moderate drinkers will feel some subtle effects at this level.

After a man has one standard drink

  • If he weighs 100 pounds, he will have a Blood Alcohol Concentration of 0.04. If he drinks it over one hour, he will have a Blood Alcohol Concentration of 0.02, and if he drinks it over two hours, he will have a Blood Alcohol Concentration of 0.01. Only after three hours will he have a Blood Alcohol Concentration of 0.00.
  • If he weighs 150 pounds, he will have a Blood Alcohol Concentration of 0.03. If he drinks it over one hour, he will have a Blood Alcohol Concentration of 0.01, and after two hours, he will have a Blood Alcohol Concentration of 0.00.
  • If he weighs 200 pounds, he will have a Blood Alcohol Concentration of 0.02. If he drinks it over one hour, he will have a Blood Alcohol Concentration of 0.003, and after two hours, he will have a Blood Alcohol Concentration of 0.00.

So after just one drink, even larger men take around two hours for their Blood Alcohol Concentration to return to zero.

Two Drinks

Two American standard drinks will, on average, produce a Blood Alcohol Concentration of about 0.04, and most light and moderate drinkers will feel relaxed at this level. Even if you don't feel the effects of alcohol intoxication, reaction times will be slowed, and fine motor skills will be affected to the extent that driving will be impaired.

After a man has two standard drinks…

  • If he weighs 100 pounds, he will have a Blood Alcohol Concentration of 0.08. If he drinks them over one hour, he will have a Blood Alcohol Concentration of 0.06, and if he drinks them over two hours, he will have a Blood Alcohol Concentration of 0.04. After three hours, his Blood Alcohol Concentration will be down to 0.03, after four hours, it will be down to 0.01, and only after five hours will he have a Blood Alcohol Concentration of 0.00.
  • If he weighs 150 pounds, he will have a Blood Alcohol Concentration of 0.05. If he drinks them over one hour, he will have a Blood Alcohol Concentration of 0.04, and after two hours, he will have a Blood Alcohol Concentration of 0.02. After three hours, his Blood Alcohol Concentration will be down to 0.003, and after four hours, it will be down to 0.00.
  • If he weighs 200 pounds, he will have a Blood Alcohol Concentration of 0.04. If he drinks them over one hour, he will have a Blood Alcohol Concentration of 0.004, and after two hours, he will have a Blood Alcohol Concentration of 0.00.

So after two drinks, it takes four to six hours for your Blood Alcohol Concentration to return to zero.

Three Drinks

Three American standard drinks will produce, on average, a Blood Alcohol Concentration of about 0.06. The negative effects of alcohol start to show, judgment will be impaired, often affecting people’s ability to make rational decisions, particularly around risk taking activities such as driving and continuing to drink.

Perception, learning, memory, coordination, sexual arousal, alertness and self-control will also be impaired.

After a man has three standard drinks…

  • If he weighs 100 pounds, he will have a Blood Alcohol Concentration of 0.11. If he drinks them over one hour, he will have a Blood Alcohol Concentration of 0.10, and if he drinks them over two hours, he will have a Blood Alcohol Concentration of 0.08. After three hours, his BAC will still be at 0.07, and after four hours, it will be at 0.05. After five hours, it will be down to 0.03, after six hours, it will be at 0.02, and after six hours, it will be at 0.001. Only after a whopping seven hours will he have a Blood Alcohol Concentration of 0.00.
  • If he weighs 150 pounds, he will have a Blood Alcohol Concentration of 0.08. If he drinks them over one hour, he will have a Blood Alcohol Concentration of 0.06, and after two hours, he will have a Blood Alcohol Concentration of 0.04. After three hours, his Blood Alcohol Concentration will be down to 0.03, and after four hours, it will be down to 0.01. By five hours, it will be down to 0.00.
  • If he weighs 200 pounds, he will have a Blood Alcohol Concentration of 0.06. If he drinks them over one hour, he will have a Blood Alcohol Concentration of 0.004, and after two hours, he will have a Blood Alcohol Concentration of 0.02. After three hours, his Blood Alcohol Concentration will be down to 0.01, and after four hours, it will be down to 0.00.

Six Drinks

The effects noted at the three drink level (or a Blood Alcohol Concentration of 0.06) will become more pronounced with each additional drink. At six drinks, which will produce, on average, a Blood Alcohol Concentration of about 0.12, vomiting usually occurs, unless this level is reached slowly, or you already have tolerance to alcohol. Vomiting is the body’s first line of defense against overdose.

  • This Blood Alcohol Concentration level would be reached by a 100-pound man quickly, by drinking three drinks in less than one hour, or four drinks over two hours.
  • A 150-pound man would reach this level consuming six drinks over two to three hours.
  • A 200-pound man would reach this level if he drank six drinks in less than one hour. If these people drank more slowly, it might take eight or nine drinks to reach this level over two or three hours.

Seven to Eight Drinks

At the point where your Blood Alcohol Concentration reaches 0.15, you have the equivalent of half a pint of whisky circulating in your bloodstream. Most people have difficulty walking in a straight line at this point.

Ten Drinks

With a Blood Alcohol Concentration of 0.2, most people experience a “blackout,” having no memory of all or part of what happened during the period their Blood Alcohol Concentration was at this level. In younger people, this level can be fatal.

Fifteen Drinks

At the Blood Alcohol Concentration level of 0.3, most people lose consciousness.

Twenty Plus Drinks

The Blood Alcohol Concentration level of 0.45 is the average fatal dose for adults, at which point breathing and heartbeat stop.

So, How Much To Drink?

In general, three drinks or more will produce negative effects. These negative effects will increase the more you drink, and the more quickly you drink. However, because your perception, impulsiveness and self-control are inhibited, you may not be aware of how badly you are impaired. These effects are particularly pronounced in smaller, lighter men.

If sticking to two drinks doesn’t seem worth it, or if you don’t think you can stick to just two drinks, then you might be better off if you didn’t even bother drinking.

That way, you would not have to worry about driving home, or about problems caused by intoxication. It is also worth knowing that the majority of sexual assaults occur when one or both people have been drinking. So having more than three drinks at a bar, club or party may leave you particularly vulnerable to this.

Source:

Miller, W. and Munoz, R. Controlling Your Drinking: Tools to Make Moderation Work For You. New York: Guilford. 2005.

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