A legal measurement of alcohol concentration in the bloodstream, determining whether a person is considered legally impaired or intoxicated. The blood alcohol level is usually stated as a percentage, such as 0.10%. In most U.S. states, this is a measurement of "weight by volume" (w/v). 0.10% w/v is equivalent to 100 milligrams of alcohol per deciliter (100 milliliters) of blood, which is the same as 1 gram per liter (g/L). In a few states, the measurement is the percentage mass concentration (w/w, or milligrams of alcohol per milligram of blood). 0.10% w/w is the same alcohol concentration as 0.1055% w/v or 1.055 g/L, a slightly higher concentration than 0.10% w/v. Internationally, blood alcohol levels are often stated in millimoles per liter (mmol/L). 1 millimole per liter is equal to 4.61 mg/dL or 0.00461% w/v. In the other direction, each 0.01% w/v is equal to about 2.169 mmol/L