Blood alcohol level, also referred to as blood alcohol content (BAC), is a measurement of milligrams of alcohol in every 100 milliliters of blood. An individual with a BAC of 0.08% (the legal limit) has 80 milligrams of alcohol in every 100 milliliters of blood.
Blood alcohol levels can be determined using a breathalyzer or blood test. Generally, the faster you drink, the higher your BAC will rise. Other factors can influence BAC, including body composition, gender, medications, and general health.