What Does Blood Alcohol Concentration (BAC) Mean?

Blood alcohol concentration (BAC) is the percent of alcohol in a person’s bloodstream. Some factors that affect BAC, like whether you chug drinks or sip them, are completely under your own control. Other factors, like your body type, you have no control over. You can
use this tool to calculate your BAC.

What Affects BAC?

Gender

Women typically don’t metabolize (break down) alcohol as fast as men. This means that women will reach a higher BAC if they consume alcohol at a similar rate as a similarly-sized male. This is for a few reasons: 

  • Women have a lower amount of alcohol dehydrogenase—the enzyme that breaks down alcohol—in their stomach compared to men. 
  • Alcohol is water soluble, and women have a lower water content compared to men. 

Body Type

Larger persons will have a lower BAC, compared to another person of the same gender who weighs less, even if they consume the same amount of alcohol across the same time-period. Consider this: if you pour the same amount of sugar into a 12 oz glass of lemonade and a one-gallon container of lemonade, which would be sweeter? The smaller container. While the sugar content is the same in both containers, it is more concentrated in the smaller container. 

Alcohol Content 

The higher the alcohol by volume (ABV) in a drink, the higher BAC it will produce. For example, a 2 oz. pour of a 100-proof beverage has more alcohol than a 2 oz. pour of an 80-proof beverage. Keep in mind that different beer styles and brands can have vastly different ABV—most beers fall into the 4% to 7% ABV range, but some are lower and some are higher than that. You can check the label on your beverage to determine the ABV. 

Be wary of “trash can punch” or similarly mixed drinks that contain extremely high ABV because they contain a number of different kinds of alcoholic beverages and are not mixed with any degree of predetermined measurement. You also can’t check the label to figure out the ABV percentage of the drink. 

Size of Drink

A larger drink of the same alcohol content will contain more alcohol and produce a higher BAC than a smaller drink. For example, a 24 oz beer has twice the alcohol of the same 12 oz beverage. 

Time Spent Drinking

The faster you consume alcohol, the faster your BAC will rise. For instance, if a person consumed a 6-pack of beer in 3 hours, they will have a lower BAC than if the same 6-pack is consumed in 1 hour. 

Food

Food slows the absorption of alcohol into the bloodstream by keeping alcohol in your stomach longer than if you drink on an empty stomach. However, this is a “pay me now or pay me later” situation—the alcohol will eventually reach the bloodstream. 

Carbonation

Carbonated drinks, such as champagne or sparkling wine, as well as mixed drinks containing carbonated mixers like soda, may increase the speed at which alcohol passes through the stomach and result in a higher BAC.