Monday, May 20, 2013

How to Blow a .08

The National Traffic Safety Board announced last week that it is recommending lower standards for drunk driving in all 50 states and requesting to move the threshold from .08% to .05%.

We've all seen the commercials and the billboards - .08 Don't Blow It. What does that mean though?

BAC is the Blood alcohol content of a person's blood, expressed in a percentage. If a person has a BAC of .10, then one-tenth of one percent of a person's blood, by volume, is alcohol. Obviously, the higher the number the higher the percentage of alcohol volume in a person's blood.

I'll post on the reasons behind the current law and the motives to change it later this week, but today I wanted to give you a glimpse into how BAC is calculated based on forensic toxicology.

Every alcoholic drink increases a person's blood alcohol. A drink is a regular size beer, shot, or glass of wine. The amount it increases blood alcohol depends on a number of factors like gender, body weight, food consumed, metabolic rate, and frequency of drinking. We'll look at a 180 pound man who is drinking normally and has not eaten.

I'm certain that I'll get some messages from people explaining how wrong the science behind all this, but so be it. Generally, one drink will increase a person's BAC .02. Click here to see a chart.

How many drinks to get to a .08?

1 Hour:


Four drinks in an hour will get a person to .08. But the moment you start hitting the bottle, your body begins processing and eliminating the alcohol from the blood. After this point, we have to start factoring in how much alcohol is eliminated in an hour. Generally, around .015, or .015% is eliminated an hour. Basically, one drink an hour is eliminated from your body.

A person is under the current legal limit.

2 Hours:


You were at the .08 from the four drinks the first hour. But the body is still getting rid of the booze. Add in another .02 for the extra drink, but your body has gotten rid of a drink and a half at this point (.015 per hour or .3 for two hours).

At 5 drinks, a person is under the legal limit, but toeing the line.


6 drinks takes the total to .09, above the legal limit.

3 Hours:


Another beer for 7 total (.02) and another elimination (.015).

6 beers in 3 hours? .075

4 Hours:


Another .02 added and another .015 subtracted.

7 Beers in four hours? .08

These are just rough calculations to show you how much a person needs to drink to get to the current legal limit. Remember a person can still be intoxicated at any number if the alcohol has impaired them enough that they shouldn't be driving a car.


  1. "If a person has a BAC of .10, then 10% of a person's blood, by volume, is alcohol."

    BAC is already reported as a percentage, so a BAC of .10 means that a person's blood, by volume, is one-tenth of one-percent alcohol.

    Since you presumably prosecute alleged drunk drivers, can you explain why you think that it could possibly be reasonable for someone to have 10% of their blood volume be alcohol and still be alive? Do your police officer witnesses have any better common sense then this?

  2. A BAC of .10 means .1 percent of your blood is alcohol, not 10 percent.

    1. Wrong. You multiply decimals by 100 to make them percents.

  3. Actually, the conversion from .10 to blood volume is 1 part alcohol to 1000 blood. So .10 blood alcohol doesn't mean 10% of the blood volume is alcohol (you would certainly be dead from that level). It actually means you have about .001 liters of alcohol on board (.0001 of 10 liters blood).

  4. Absolutely correct. I'm sorry for not picking that up before publishing. Thank you for catching it and it has been updated.

  5. First article encountered with good content on subject. Thanks.

  6. for an average person it takes about blank drinks to reach the blood alcohol level of point 10

  7. how many drinks does it take two reach .10

  8. how many shots of vodka before you reach .08

  9. If a person is even slightly intoxicated he shouldn't be driving a car. If you are facing charges, the goal of DUI Lawyer is to avoid court proceedings which will waste much of your time and you will be declared not guilty after the arraignment. My brother works with a DUI lawyer and have told me how a good lawyer can impact outcome of any case to a great extent.

  10. If it says on the paper the first time i blew it was 180 what does that mean how over is that im so confused

    1. I am unable to answer questions about active cases, unfortunately.

  11. male 150 had 7 in four hour. can drinking water for two hour after you stop drinking help or make it worse

  12. Ladies,,, eating is paramount to lowering your bac. Don't take six shots at 8 pm and expect to be passing at even noon the next day. You must eat a bunch of "soaking up carbs" and run/steam it out. For real. You can feel normal and blow wrong well into the next day.

  13. I can't walk well after only two beers. Could I legally drink 3 and drive (225lb male)

  14. How much has someone that blew .028 had to drink?

  15. In these hypothetical scenarios, what alcohol percentage is the beer itself? 5%?