The Blood Alcohol Calculator

The BAC calculator is based on the widmark method of calculating blood alcohol content. The BAC calculator provides an accurate estimation of an individuals BAC at a certain period in time. Like any other online BAC calculator it cannot provide results with 100% accuracy due to the many variables that come into play (see below) that can affect an individuals BAC level. While the calculator takes into account age, gender, weight, drink amount, alcohol percentage and the period of time over which any alcohol has been consumed it, it is based on the consumption of alcohol by an average healthy human being.

What is BAC - Blood Alcohol Content?

Blood alcohol content is a measure of the amount of alcohol present in a certain amount of blood. It is usually described as the the amount of alcohol in mg per 100ml of blood. The prescribed legal drink driving limit in the UK is 80mg/100ml blood or 0.08%. Other countries in the world have different legal limits. It is a criminal offence to drive above the prescribed legal limit.


Numerous factors can affect an individuals BAC, these include:

  • The amount of alcohol a person consumes, the more they drink, the higher their BAC will become
  • The speed at which a person consumes alcohol, the faster a person drinks, the faster their BAC will rise
  • A persons gender. Alcohol is highly water soluble and a persons BAC is directly proportional to their total body water content. Females generally have less water in their bodies than males, this means that a female who drinks exactly the same amount of alcohol as a male, in the same space of time, will generally have a higher BAC.
  • A persons weight. The more a person weighs generally means the more water they will have in their bodies, meaning any alcohol ingested will produce a lower alcohol to blood ratio than that of a person weighing less. This is because the alcohol is "spread out" more "thinly".
  • A persons fat/muscle content. Fatty tissue does not absorb alcohol very well, alcohol will be absorbed a lot more into other tissues which are rich in water such as muscle. If two people weighing 90kg, one a tall thin person and the other a small fat person consumed the same amount of alcohol, the small fat person would have a higher BAC than the thin person.
  • A persons metabolism (the rate at which alcohol is processed and eliminated by the body). This can vary from person to person, however, the average person will eliminate 15ml of alcohol per hour. Heavy drinkers may have more active livers and can therefor eliminate more alcohol than average. People with liver disease may have less active livers and will therefor eliminate alcohol slower. Medication and the amount of food in the stomach can also have an effect on the rate at which alcohol is absorbed into the body and subsequently eliminated. Younger people also tend to metabolise alcohol more quickly than older people.



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