Name (BAC) for the amount of alcohol contained in venous blood, expressed in milligrams per gram or per milliliters (1 per mille = 1 gram of alcohol in 1 kilogram of blood or 1 mg / gram). The measurement is carried out in serum (blood without blood cells and coagulation factors) and is converted to blood content. For the determination of blood alcohol, the enzyme ADH (Alcohol dehydrogenase) used. The Swedish chemist Univ. Prof. Erik Widmark (1889-1945) developed in 1922 the named after him "Widmark's formula" for the determination of the BAK. In addition to the Widmark formula, there are other also named after the "inventors" calculation method (Seidel, Ullrich, Watson), which take into account body weight and gender and body length and age. The Widmark formula is used as the basis for electronic BAK terminals.
With the help of Widmark's formula, the blood alcohol content can be calculated with an accuracy of plus / minus 0.1 per thousand: c = A / (r * G)