Blood alcohol content (BAC) is the amount of alcohol in the bloodstream. If someone were to have a BAC of .10, this would mean that one-tenth of 1% of the blood in their body is alcohol. The more alcohol a person consumes the more intoxicated and impaired they become. The alcohol percentage is determined by the amount of alcohol consumed, the time in which the alcohol was consumed, and body weight. Eating prior to, or while drinking, may also temporarily influence BAC, reducing its effects.

Here is a BAC calculator. 

This information comes from here and here.

Euphoria (BAC = 0.03 to 0.12 percent)

They may become more self-confident or daring.
Their attention span may shorten.
They may look flushed.
Their judgement may not be as sharp and they may be more impulsive; they might say the first thought that comes to mind, rather than an appropriate comment for the given situation.
They may have trouble with fine movements, such as writing or signing their name.

Excitement (BAC = 0.09 to 0.25 percent)

They could become sleepy.
They might have trouble understanding or remembering things (even recent events).
They might not react to situations as quickly.
Their body movements may become uncoordinated.
They may begin to lose their balance easily.
Their vision could become blurry.
They may have trouble sensing things (hearing, tasting, feeling, etc.).

Confusion (BAC = 0.18 to 0.30 percent)

They are likely to be confused — they may not know where they are or what they are doing.
They may be dizzy and stagger on their feet.
They might be highly emotional, aggressive, withdrawn, or overly affectionate.
They may not see clearly.
They may be sleepy.
They likely have slurred speech.
They may have uncoordinated movements (trouble catching an object thrown to them).
They may not feel pain as readily as a sober person.

Stupor (BAC = 0.25 to 0.4 percent)

They may barely be able to move at all.
They may not be able to respond to stimuli.
They may be unable to stand or walk.
They may vomit.
They may lapse in and out of consciousness.

Coma (BAC = 0.35 to 0.50 percent)

They are unconscious.
Their reflexes are depressed (i.e. their pupils do not respond appropriately to changes in light).
Their skin feels cool to the touch (lower-than-normal body temperature).
Their breathing slows and becomes more shallow.
Their heart rate may slow.
Their life could be in danger.

Death (BAC more than 0.50 percent)

The person usually stops breathing and dies.

Binge drinking is defined as consuming 4/5 or more drinks in a 2-hour span reaching a blood alcohol content (BAC) of .08 or higher. College students binge-drink at higher rates than young people the same age who don’t attend college. Some students go to college with a lot of past drinking experience. For others, college is a time of new freedom. For students who binge-drink, getting drunk is often the main goal. And getting drunk can lead to many other dangers. These include dizziness, loss of coordination, diarrhea, vomiting, lack of judgment, or even passing out. If a person vomits when passed out, the airway can become blocked. The result can be death.

To avoid binge drinking, use the MAPP tips!

Every day, 29 people in the United States die in motor vehicle crashes that involve an alcohol-impaired driver. This is one death every 50 minutes. Source here. 

More information from the CDC here. 

To prevent impaired driving, everyone can:

• Choose not to drink and drive and help others do the same. Even one or two drinks over an hour can cause impairment.
• Before drinking, designate a non-drinking driver when with a group.
• If out drinking, get a ride home or call a taxi.
• Don’t let friends drink and drive.
• Choose not to binge drink themselves and help others not to do it.
• Talk with a doctor or nurse about drinking and driving and request counseling if drinking is causing health, work, or social problems.
• Buckle up every time, no matter how short the trip. Encourage passengers in the car to buckle up, including those in the back seat.

There is no known safe amount of alcohol use during pregnancy or while trying to get pregnant. There is also no safe time during pregnancy to drink. All types of alcohol are equally harmful, including all wines and beer.

• More information from the CDC here