The legal alcohol limit when driving is based on the blood alcohol content of one's blood. The blood alcohol content (BAC) is a measure of how much alcohol is in the blood. When it exceeds a certain percentage, then it is not deemed safe to drive. There are many different factors that conclude what one's BAC is, so it can sometimes be confusing. But with such devices as breathalyzers that can be utilized on site when a person is pulled over, figuring it becomes considerably easier.

However, it is figured mathematically but is nowhere as near to accurate as the breathalyzers. If these details are known, the easiest way to figure BAC is by taking the amount of alcohol that was consumed and dividing that by the total amount of water in the body. Alcohol dehydrates the body, so if one takes into consideration that a 150 pound woman has 73.5 pounds of water in her body and uses that number to divide into the amount of alcohol consumed, one could successfully calculate their BAC and also figure out how much water their body is lacking due to alcohol consumption.

A BAC of .20% means a person is extremely intoxicated. In fact, they are so intoxicated that if they were drinking for the first time in their life, they would have never made it to a BAC of .20% because they would've passed out by .15%. A person this intoxicated is in a state in which they can, under no circumstances, operate a motor vehicle. Even at .01% a person may not pass all sobriety tests despite the fact that they look normal. However in various places around the world, the legal alcohol limit for driving varies. Some have absolutely no tolerance for it while others do to a certain extent. Sometimes the tolerance extends to just a couple of drinks to no more than the standard dose of cough syrup. That is why it is important to be vigilant about the legal alcohol limit in the area in which you are drinking, especially if you intend on driving. If you exceed the limit, then you probably need to get a cab.

The legal alcohol limit for driving throughout the world:

- The standard BAC for the United States is .08% but can vary from state to state. Operators of busses and other such carriers are allowed a BAC of .01% and pilots are allowed a BAC of .04% within 8 hours of consuming alcohol.

- United Kingdom: .08%

- France: .05%

- Germany: .05%

- Australia: .05%

- Canada has a standard BAC of .08%, but has a legal limit of .04% in Manitoba. However, drivers in Ontario with G1 and G2 licenses have a limit of zero.

- Japan: .015%

- Mexico: .08%

- Norway: .02%

- Russia: .02%

How much alcohol is left in a person's system depends on how quickly they metabolize or excrete it. Two people who have had the same amount of alcohol may not display the same reading on a BAC test. Their size and weight as well as how fast their body processes it has a huge influence. So even if a person feels fine, they may not be fine.

People have different tolerances, so it is good to always be safe rather than be sorry and risk arrest for being over the legal alcohol limit while operating a motor vehicle. Doing so can also be very hazardous. Many have been killed by others who have gone out to have a good time and not arranged a designated driver or took a cab. It is fair to say that legal alcohol limits are in place in order to keep people alive.