bacYour blood alcohol concentration, or BAC, is the amount of alcohol in your blood. For example, if your BAC is .05%, that means you have 50 milligrams of alcohol in 100 millitres of blood. Each drink you have within a certain timeframe increases your BAC.

A number of factors affect how quickly your BAC rises and drops. Body type, weight and food intake at the time of drinking can all impact your BAC. Since women tend to be smaller than men and have more fatty tissue, a woman who drinks as much alcohol as a man usually has a higher BAC.

Legal and Administrative BAC Limits

In Canada, the Criminal Code BAC limit is .08%. This is the level at which Criminal Code impaired driving charges can be laid.

It is important to realize, though, that even small amounts of alcohol can impair driving ability.

That is why just about every province and territory in Canada has administrative laws for drivers whose BACs are .05% and over. Drivers at these levels do not face criminal impaired driving charges, but they are subject to licence suspensions ranging from 24 hours to 7 days depending on the province or territory. Provincial administrative licence suspension programs also include escalating suspensions for repeat infractions, vehicle impoundments, education and remedial program requirements and alcohol ignition interlocks.

Young drivers in many provinces and territories have a .00% BAC requirement. They may range for the duration of the graduated licensing program or may extend until they are 21 years of age, depending on the jurisdiction. These special rules for young drivers reflect the very serious increased risks seen when young people mix drinking with driving.

Calculating BACs

For the vast majority of people, drinking socially – having a glass of wine or two with dinner or a beer or two after work – will not put them above the .05% level.

The safest way, always, is to separate drinking from driving entirely. If you are going to be drinking more than that, don’t risk a licence suspension or worse, a crash — plan alternate transportation home.

MADD Canada offers a BAC estimates chart to provide a general idea of how many drinks it takes to get to the 05% and .08% BAC levels.