Abstract: This invention relates to apparatus for estimating body alcohol concentration from personal body characteristics. For example, a calculator 10 has a keyboard 12 through which the user can input information concerning his sex, body weight, degree of fat, food consumption, alcohol consumption and the timing of these last two events. Depending on the mode into which the apparatus is set, the user can be told his maximum body alcohol concentration, how much more he may drink before reaching a legal limit, or when he may achieve the legal limit if he drinks no more.