Drink Driving .org
Drink Driving in the UK

BAC Calculator

Blood Alcohol Content Calculator

Are you male or female?

What is your weight?

Drinks Consumed


 % Abv

How Many?

Add Drink(s)


 % Abv

How Many?

Add Drink(s)


 % Abv

How Many?

Add Drink(s)

Time Since Last Drink

Hours Minutes

Reset Drinks | Start Over

Drinks added: 0 | Time Elapsed: 0 Hrs 0 mins

BAC% = waiting input

[legal limit England & Wales: 0.08%]

[legal limit Scotland: 0.05%]

No online BAC Calculator should be used to determine an individuals fitness to drive. There are so many variables and factors that can affect a specific individuals BAC level at any given time that the only fail-safe and reliable way to calculate an individuals blood alcohol level at a precise moment in time is by blood analysis or a reliable and type approved breathalyser. This BAC calculator provides reliable estimates based on average biological values and scientific research and should be used for educational, research and information purposes only. If in doubt, use common sense and do not drive.

The Drinkdriving.org Blood Alcohol Calculator

The Drinkdriving.org 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 gender, weight, drink amount, alcohol percentage and the period of time over which any alcohol has been consumed, 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 amount of alcohol in mg per 100ml of blood. The maximum prescribed legal drink driving limit in England and Wales is 80mg/100ml blood or 0.08% and in Scotland it is 50mg/100ml blood or 0.05%.

It is a criminal offence to drive with a blood alcohol level that exceeds the maximum prescribed legal limit.

Factors that Affect your BAC (Blood Alcohol Content)

Numerous factors can affect an individuals BAC, these include:

  • The amount of alcohol a person consumes: the more alcohol a person drinks, 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 person's gender: alcohol is highly water soluble and a person's 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 person's weight: the more a person weighs usually means the more water they will have in their bodies. This means 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 person's 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 usually have a higher BAC than the thin person.
  • A person's 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 usually eliminate 10ml of alcohol per hour. Heavy drinkers may have more active livers and can therefore usually eliminate more alcohol than average. People with liver disease may have less active livers and will therefore usually eliminate alcohol slower.
  • Medication and the amount of food in the stomach: this can have an effect on the rate at which alcohol is absorbed into the body and subsequently eliminated.
  • A person's age: younger people tend to usually metabolise alcohol more quickly than older people.



Top of Page