The blood alcohol concentration (BAK) is a measure of the amount of alcohol in the blood and is usually expressed by weight as g/kg (per mille). It is used to derive statements about the impairment of concentration and sanity by alcohol.
The concentration of alcohol in the blood depends on:
- the amount of alcohol consumed
- the rate of absorption of alcohol in the body
- the amount of body water in which the alcohol is distributed
- the rate of breakdown of alcohol in the blood.
Depending on how the distribution of alcohol in the body is defined, different per mille values result.
In addition to Widmark’s formula, which was historically the first and is still in use today, other calculation methods have been defined that take body length and age into account in addition to body weight and gender.