Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of

alcohol intoxication Alcohol intoxication, also known as alcohol poisoning, commonly described as drunkenness or inebriation, is the negative behavior and physical effects caused by a recent consumption of alcohol. In addition to the toxicity of ethanol, the main ...

used for legal or medical purposes; it is expressed as mass of alcohol per volume or mass of blood. For example, a BAC of 0.10 by (0.10% or one tenth of one percent) means that there is 0.10 g of alcohol for every 100 mL of blood, which is the same as 21.7 mmol/L. A BAC of 0.10 by (0.10%) is 0.10 g of alcohol per 100 g of blood (23 mmol/L). A BAC of 0.0 is sober; in different countries the maximum permitted BAC when driving ranges from about 0.04% to 0.08%; BAC levels over 0.08% are considered very impaired; above 0.4% is potentially fatal.

Effects by alcohol level

Estimation by intake

Blood alcohol content can be estimated by a method developed by Swedish professor in the 1920s: :

EBAC = \frac\times100\%-\beta\times T

where: * is the mass of alcohol consumed. * is the ratio of body water to total weight. It varies between individuals but averages about 0.68 for men and 0.55 for women, since women tend to have a higher percentage of fat. * is body weight. * is the rate at which alcohol is metabolized. It is approximately 0.017% per hour. * is the amount time during which alcohol was present in the blood (usually time since consumption began). Sometimes the above is multiplied by 1.055 g/mL, the

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...

of blood. In terms of

fluid ounce A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called ''capacity'') typically used for measuring liquids. The British Imperial, the United States customary, and the United ...

s of alcohol consumed and weight in pounds, the formula can be written as :

EBAC=8\times\text/\text-\beta\times T

for a man or :

EBAC=10\times\text/\text-\beta\times T

for a woman. Regarding metabolism () in the formula; females demonstrated a higher average rate of elimination (mean, 0.017; range, 0.014–0.021 g/210 L) than males (mean, 0.015; range, 0.013–0.017 g/210 L). Female subjects on average had a higher percentage of body fat (mean, 26.0; range, 16.7–36.8%) than males (mean, 18.0; range, 10.2–25.3%). Additionally, men are, on average, heavier than women but it is not strictly accurate to say that the water content of a person alone is responsible f