How to Calculate Blood Alcohol Level

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While the only 100 percent accurate method to determine your blood alcohol level requires a lab test, this formula can give you a general idea of how much alcohol is in your bloodstream.

Warning
Don't drink unless you're of legal age. Drink responsibly, and never drink and drive.

Step 1: Determine the number of drinks
Determine how many drinks you've had. A standard drink in the U.S. contains .6 ounces of pure alcohol.

Tip
Generally, .6 ounces of pure alcohol is found in 12 ounces of beer, 8 ounces of malt liquor, 5 ounces -- or one standard glass -- of wine, or 1.5 ounces -- one shot -- of 80-proof liquor.

Step 2: Multiply by .025
Multiply the number of standard drinks you had by .025. This will give an approximation of your percent blood alcohol.

Tip
Remember that men metabolize alcohol faster than women, and that people who weigh more absorb alcohol faster.

Step 3: Determine the time since your last drink
Determine the amount of time that has passed since you took your last drink of alcohol.

Step 4: Subtract .025 percent
Subtract .025 percent for each full hour that passed since your last drink. If 2 hours have passed since you finished your third drink, subtract .05 from 0.075 to determine an approximate blood alcohol level of .025 percent.

Step 5: Wait
To be safe, wait to drive until you calculate your blood level is back near 0. Wait at least an additional half hour if you are a woman or you weigh less than 150 pounds.

Did You Know?
Research has shown that youths who use alcohol before age 15 are 5 times more likely to become alcohol-dependent than adults who begin drinking at age 21.