The New York (BAC) Blood Alcohol Content

Blood alcohol content (BAC) or blood alcohol concentration is the concentration of alcohol in blood. It is measured either as a percentage by mass, by mass per volume, or a combination. For example, a BAC of 0.20% can mean 2 grams of alcohol per 1000 grams of an individual's blood, or it can mean 0.2 grams of alcohol per 100 millilitres of blood.

In many countries, the BAC is measured and reported as grams of alcohol per 1000 millilitres (1 litre) of blood (g/1000 mL). Because the specific gravity of blood is very close to the specific gravity of water (its main component), the numerical values for BAC (%, percent) and (g/1000 mL, permille) do not differ to any consequential degree other than the placement of the decimal point.

The number of drinks consumed is a very poor measure of intoxication largely because of variation in physiology and individual alcohol tolerance. However, it is generally accepted that the consumption from sober of two standard drinks (containing a total of 20 grams) of alcohol will increase the average person's BAC roughly 0.05% (a single standard drink consumed each hour after the first two will keep the BAC at approximately 0.05%), but there is much variation according to body weight, gender, and body fat percentage. Furthermore, neither BAC nor the number of drinks consumed are necessarily accurate indicators of the level of impairment. Tolerance to alcohol varies from one person to another, and can be affected by such factors as genetics, adaptation to chronic alcohol use, and synergistic effects of drugs.

Alcohol content in blood can be directly measured by a hospital laboratory. More commonly in law enforcement investigations, BAC is estimated from breath alcohol concentration (BrAC) measured with a machine commonly referred to as a Breathalyzer.