Know Your Blood Alcohol Level (BAL)

A number of factors affect BAL including:

Weight. The more you weigh the more area alcohol has to go, and thus, the lower the concentration of alcohol in your body.

Body Fat. The higher your percent body fat the higher your BAL compared to someone of equal weight with less body fat. This occurs because fatty tissue absorbs 60-70% less water.

Gender. Women absorb about 5 - 10% more alcohol than men. In addition, women tend to weigh less and have a higher percentage of body fat, and thus have higher BALs.

Metabolism. While the rate at which alcohol is eliminated by the liver (1 standard drink per hour) is very similar for all people, it is affected by tolerance. Tolerance results in an increase in the elimination rate. This may surprise you, but tolerance is mostly a behavioral and neural adaptation to alcohol that has little to do with BAL.

Considering these factors we can only estimate BAL.

Think About "Standard Drinks"

The key to knowing the amount of alcohol you consume is to think in terms of “standard drinks”.

A standard drink is 0.5 oz. of pure alcohol.

This value was selected because, on average, a person’s liver can process 0.5 ounces of alcohol in one hour. This makes it easy to determine how many drinks are still in your system. For example, if you consumed 5 standard drinks over 3 hours, you would have 2 standard drinks yet to be processed by your liver.

To calculate standard drinks multiple drinks size (in ounces) by the percent alcohol by volume, and then divide by ½:

(Size of Drink  X  Alcohol Content)   /   ½.

Your can also use this simpler formula:

Size of Drink   X   Alcohol Content   X  2.

Estimating Your BAL

The average person can eliminate one standard drink per hour (slightly faster for those with tolerance). The amount one standard drink will raise your BAL depends on weight and percent body fat; but on average, one standard drink will raise a women's BAL by .020 and a man's BAL by .017.

To Estimate BAL:

1. Take the number of standard drinks consumed and subtract the number of hours you have been drinking.
   
2. Then multiply that number by either .02 or .017.
   

EXAMPLE: 5 standard drinks in three hours would be:
For a 170lb man: (5 drinks – 3 hours) x .017 = .034.
For a 130lb women: (5 drinks – 3 hours) x .02 = .04.

For a more accurate estimate, you can use one of the many calculators available on the web. These calculators also consider weight.

To find a BAL calculator on the web:
Google™ “blood alcohol level” or “blood alcohol concentration” and “calculator.