Many Motorists Ask: “How Do I Know If I’m Over The Legal Limit?”


Most Minnesota motorists are aware that a blood alcohol level of .08 is evidence of legal intoxication under state law. Therefore, drivers often ask themselves, “How do I know if I’m over the legal limit?”

A report from the Centers for Disease Control and Prevention (CDC) addresses this very question, and it discusses the impact of various blood alcohol concentration (BAC) levels on driving.

A Standard Alcoholic Drink Defined

In its report, the CDC provides specific information linking the rate and amount of alcohol consumption to BAC. It calculates the number of standard drinks that a 160-pound man would have to consume in one hour to reach various BAC levels. The CDC defines a “standard drink” as one containing 0.6-oz of pure alcohol. According to the agency, this is the amount of alcohol found in:

  • 5-oz of wine with a 12-percent alcohol content
  • 12-oz of beer with a 5-percent alcohol content
  • 8-oz of malt liquor with a 7-percent alcohol content
  • 1.5-oz (a “shot”) of 80 proof liquor like vodka, whiskey or rum

It’s important to understand that the effects of alcohol consumption on BAC does vary based upon weight, gender and other factors, so this is only a general guideline.

Alcohol’s Impact on Driving

The report links the number of standard alcoholic drinks consumed to their impact on driving ability:

Two standard drinks – The CDC goes on to predict how much different alcohol levels will impact driving. For example, two alcoholic drinks, as defined above, would result in an approximate BAC of .02%. This BAC level is linked to a decline in visual function, including the ability to rapidly track a moving target. This blood alcohol level is also linked to a reduced ability to multi-task. That is, to perform two tasks at the same time.

Three standard drinks – Three alcoholic drinks consumed in one hour, as defined above, results in a BAC of about .05%. This alcohol level further reduces the ability to track moving objects. Also, reduced coordination may impact one’s ability to steer. Overall, there is a discernible reduction in the ability to respond to driving emergencies.

Four standard drinks – Four such drinks consumed by a 160-lb man in one hour results in a BAC of .08%, the legal DWI threshold in most jurisdictions. This level of intoxication is associated the reduced abilities noted above, along with a reduced ability to concentrate, control speed and process information. The latter impairment reduces the motorist’s ability to detect signals and to conduct visual searches. A .08% BAC is also associated with short-term memory loss and impaired perception.

Five standard drinks –¬†Five drinks consumed in an hour elevates BAC to about .10%. At this level of impairment, a motorist experiences the limitations noted above, plus a decreased ability to brake properly and to maintain proper lane position.

Seven standard drinks – In a 160-lb man, seven drinks consumed in an hour will yield a BAC of .15%, almost double the legal threshold. At this BAC level, there is substantial impairment to information processing, vehicle control and attention to driving in general. Those with a BAC of .15% will often experience significant loss of balance and vomiting. How quickly will alcohol dissipate in the blood stream? One guideline suggests that BAC levels will decrease approximately .015 every hour after the alcohol is consumed. For example, if one drinks to the point of having a BAC of .10, it would take two hours for that level to decrease .03 (2 x 015) to .07.

Ultimately, there are just too many BAC variables and too many safety risks for a driver to take a chance on a DWI arrest.

We want you and your family members to remain safe on the road, and to avoid a DWI arrest. To learn more about our legal services, including DWI and criminal defense, please contact us.

Disclaimer: The content of this article does not constitute an attorney-client relationship. Please contact Jennifer Speas to discuss the specifics of your case.