[header] How to calculate blood alcohol level [title] Understand what blood alcohol content (bac) means. [step] Blood alcohol content is a measurement of the amount of alcohol in your body. So, a bac of 0.10% means 1 part alcohol for every 1000 parts of blood. 
It is often used for legal or medical purposes, like when determining if you've had too much to drink and drive. [substeps] A bac of 0.08%, often the legal level, indicates that you have 80 mg of alcohol per 100ml of blood in your body.