University of Rochester

University Health Service (UHS)
Health Promotion Office

Understanding Blood Alcohol Content (BAC)

Blood Alcohol Content (BAC) refers to the milligrams of alcohol per 100 milligrams of blood, usually expressed as a percentage. In other words, .10 BAC is 1 part alcohol for every 1,000 parts blood. An absolute BAC can only be obtained by drawing a sample of blood. As that method is not always practical, the best way to determine a reliable estimate is by using a breathalyzer that takes a sample of alveolar (deep lung) air. Handheld breathalyzers are slightly less accurate, but are more convenient.

Alcohol's Biphasic Effect

As BAC slowly rises and is under .06%:

At a BAC of .06%:

As BAC surpasses .06%:

Once the drinker has gone beyond the "Point of Diminishing Returns," it is impossible to return to the Buzz Zone. Remaining in the Buzz Zone maximizes the drinker's positive experience and reduces harm. Tolerance (being able to "hold one's liquor") hampers alcohol's positive effects by reducing the initial stimulant qualities (yellow line). High tolerance makes drinking more costly in terms of calories and money, limits the euphoria, and worsens the depressant effects.

How much do you really drink?

One of the biggest problems with self-determining one's BAC is that few students keep track of how many drinks they actually consume. A standard drink contains oz of alcohol, regardless of the quantity of surrounding liquid or sugar. Some alcoholic beverages are labeled with a percent alcohol by volume, but most beers are not. A general rule of thumb is that the darker and/or more bitter the beer, the more alcohol the beverage contains. With the exception of Chardonnay, red wines have a higher alcohol content than whites, and sweeter wines tend to have a lower alcohol content than dry wines. In similar fashion, dark liquor tends to have a higher alcohol content than light or clear liquor, and sweet liquor tends to have a lower alcohol content than dry liquor. Use the following chart to determine how much alcohol is in your favorite drink.

Percent Alcohol By Volume
Type of Drink Percent Alcohol
Average (Range)
Beer (Lager)    
Light 4.2 (3.8 - 4.4)
Regular 4.5 (4.1 - 4.9)
Ice 5.5 (5.0 - 5.9)
Ales 4.5 (4.0 - 6.0)
Porters/Stouts 6.5 (6.0 - 8.0)
Wines 12.0 (7.1 - 14.2)
Chardonnay 12.5 (11.0 - 14.0)
Other Whites 10.0 (7.1 - 12.0)
Red Wines 13.0 (12.0 - 14.2)
Vodka 40.0 (40.0 - 50.0)
Gin 42.5 (40.0 - 48.5)
Rum 45.0 (40.0 - 95.0)
Tequila 45.0 (45.0 - 50.5)
Brandy 42.0 (40.0 - 43.0)
Whiskey 50.0 (40.0 - 75.0)
*Chart adapted from Virginia Tech,

Alcohol Myopia

Alcohol Myopia literally means "cognitive nearsightedness", and refers to alcohol's ability to substantially decrease reasoning abilities, judgment, and the ability to concentrate. At BACs above 0.06 many individuals begin to focus exclusively on obvious cues and signals, and fail to take into account peripheral information and long-term consequences. Affected individuals literally zone in on one particular emotion or person, and lose sight of their surroundings. As a result, affected individuals may misperceive social cues and act inappropriately. While an intoxicated individual's lack of social perception may be humorous to a sober on-looker, failure to appropriate read social signals puts both individuals at risk, and can lead to serious, life-changing consequences. Remember that intoxication is not an excuse for inappropriate or illegal behavior, and that you are responsible for your actions at all times.

Progressive Effects of Alcohol

When most people think about alcohol, they first think about the "buzz" or mild "up" feeling that occurs when a individual consumes moderate amounts of alcohol over a corresponding period of time (ex: one drink per hour for up to four hours consecutively). While alcohol can produce a positive, relaxed overall feeling, alcohol can also produce a series of negative feelings. Many people incorrectly assume that the more alcohol they consume the better they will feel. However, that simply is not the case. There comes a point, called the point of diminishing returns, when the "buzz" will not increase with more alcohol. In fact, at this point, (typically around a BAC of .06), drinking more alcohol is almost guaranteed to lead to a series of negative effects such as fatigue, impaired sexual performance, inappropriate social responses and behavior, and/or over-expressed emotions.

Known as the biphasic effect or biphasic response, these up and down feelings can be avoided by drinking slowly to a maximum BAC of 0.06%. See below How to Maximize the Positive Effects of Alcohol for more information.

Blood Alcohol
Changes in Feelings
and Personality
Physical and Mental
0.01 - 0.06 Relaxation
Sense of Well-being
Loss of Inhibition
Lowered Alertness
0.06 - 0.10 Blunted Feelings
Impaired Sexual Pleasure
Reflexes Impaired
Depth Perception
Distance Acuity
Peripheral Vision
Glare Recovery
0.11 - 0.20 Over-Expression
Emotional Swings
Angry or Sad
Reaction Time
Gross Motor Control
Slurred Speech
0.21 - 0.29 Stupor
Lose Understanding
Impaired Sensations
Severe Motor Impairment
Loss of Consciousness
Memory Blackout
0.30 - 0.39 Severe Depression
Death Possible
Bladder Function
Heart Rate
0.40 and greater Unconsciousness
Heart Rate
*Chart adapted from Virginia Tech,

How to Maximize the Positive Effects of Alcohol

An individual maximizes the positive effects of alcohol when s/he is able to keep his/her BAC at or below .06. Known as the "Pleasure Zone", a consistent BAC below .06 can significantly reduce the potential negative outcomes of drinking. The problem with this method is that, as discussed in Understanding BAC, it is near impossible to know one's own BAC without using an external device such as a breathalyzer. However, that doesn't excuse mindless imbibing. It is recommended that individuals consume no more than one drink per hour for up to four hours consecutively. This moderate level of alcohol intake will enable an individual to benefit from the positive effects of alcohol for a longer period of time than if you consumed all four drinks at once, thereby maximizing one's time in the Pleasure Zone.


BAC Calculator

For more information, contact Linda Dudman in the UHS Health Promotion Office at (585) 273-5770 or

Please send questions about the technical structure/operation to the UHS Web Master

Last modified: Wednesday, 27-May-2015 16:45:29 EDT