Gigra BAC Calculator - Version 1.0 Blood alcohol concentration (BAC) is the amount of alcohol in an individual's body, measured by the weight of the alcohol in a volume of blood. The BAC limit determines the maximum amount of alcohol that can be consumed before it is illegal to operate a motor vehicle on a public road.Our BAC Calculator is designed to estimate your BAC level. However, your actual BAC will vary depending on a host of different factors, such as your hydration status, recent meals, fluid intake, kidney function, and much more.Use this software as BAC estimation tool only.