blood alcohol content blood alcohol content blood alcohol content (bac), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication 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 volume (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 mass (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 0.02% to 0.08%; bac levels over 0.08% are considered impaired; above 0.40% is potentially fatal. blood alcohol contentethanolsynonymsblood alcohol concentration, blood ethanol concentration, blood alcohol level, blood alcohol concentration, blood alcoholloinc5639-0, 5640-8, 15120-9, 56478-1 effects by alcohol level further information: short-term effects of alcohol consumption as bac increases, the short-term effects of alcohol become more perceptible. at low levels of impairment (bac 0.01–0.05%), people may experience mild relaxation and reduced social inhibition, along with impaired judgment and coordination. at higher levels of impairment (bac 0.06–0.30%), the effects become more pronounced and may include impaired vision and hearing. at extremely high levels (bac 0.40% or higher), a person may experience a loss of consciousness, impaired breathing, and a drop in body temperature that can lead to hypothermia or organ failure. estimation by intake blood alcohol content can be estimated by a method developed by swedish professor erik widmark in the 1920s: e b a c = a r × w t × 100 % − β × t \times 100\%-\beta \times t} where: a is the mass of alcohol consumed. r 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. wt is body weight. β is the rate at which alcohol is metabolized. it is approximately 0.017% per hour. t 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 of blood. in terms of fluid ounces of alcohol consumed and weight in pounds, the formula can be written as e b a c = 8 × fl oz / weight in pounds − β × t /-\beta \times t} for a man or e b a c = 10 × fl oz / weight in pounds − β × t /-\beta \times t} for a woman. regarding metabolism (β) 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 for the dissolution of alcohol within the body, because alcohol does dissolve in fatty tissue as well. when it does, a certain amount of alcohol is temporarily taken out of the blood and briefly stored in the fat. for this reason, most calculations of alcohol to body mass simply use the weight of the individual, and not specifically their water content. examples: 80 kg male drinking 2 drinks of 14 grams (0.014 kg) each, in two hours: e b a c = ( 2 × 0.014 ) / ( 0.68 ⋅ 80 ) × 100 % − ( 0.015 ⋅ 2 ) ≈ 0.021 % 70 kg woman drinking 1.5 drinks of 14 grams each, in two hours: e b a c = ( 1.5 × 0.014 ) / ( 0.55 ⋅ 70 ) × 100 % − ( 0.017 ⋅ 2 ) ≈ 0.021 % by standard drinks main article: standard drink united states standard drinks of beer, malt liquor, wine, and spirits compared. each contains about 14 grams or 17.7 ml of ethanol. the examples above define a standard drink as 0.6 fluid ounces (14 g or 17.7 ml) of ethanol, whereas other definitions exist, for example 10 grams of ethanol. approximate blood alcohol percentage (by volume)based on one drink having 0.5 us fl oz (15 ml) alcohol by volume drinks sex body weight 40 kg90 lb 45 kg100 lb 55 kg120 lb 64 kg140 lb 73 kg160 lb 82 kg180 lb 91 kg200 lb 100 kg220 lb 109 kg240 lb 1male–0.040.030.030.020.020.020.020.02 female0.050.050.040.030.030.030.020.020.02 2male–0.080.060.050.050.040.040.030.03 female0.100.090.080.070.060.050.050.040.04 3male–0.110.090.080.070.060.060.050.05 female0.150.140.110.100.090.080.070.060.06 4male–0.150.120.110.090.080.080.070.06 female0.200.180.150.130.110.100.090.080.08 5male–0.190.160.130.120.110.090.090.08 female0.250.230.190.160.140.130.110.100.09 6male–0.230.190.160.140.130.110.100.09 female0.300.270.230.190.170.150.140.120.11 7male–0.260.220.190.160.150.130.120.11 female0.350.320.270.230.200.180.160.140.13 8male–0.300.250.210.190.170.150.140.13 female0.400.360.300.260.230.200.180.170.15 9male–0.340.280.240.210.190.170.150.14 female0.450.410.340.290.260.230.200.190.17 10male–0.380.310.270.230.210.190.170.16 female0.510.450.380.320.280.250.230.210.19 subtract approximately 0.01 every 40 minutes after drinking. binge drinking