Once in the bloodstream, alcohol leaves the system in two ways:
10% leaves through breath, perspiration, and the urine.
90% is metabolized (broken down in the body).
Pretty much everyone, regardless of age, size, or race, metabolizes alcohol at the same pace. That pace is .015 of blood alcohol concentration (BAC) per hour. So that means for every hour you are not drinking, .015 of the alcohol in your body is being metabolized and disappearing from your body (thanks to David J. Hanson, Ph.D. for this information). So, if your BAC was 0.08 (legally impaired), it would take about 5.33 hours for the alcohol to be eliminated from your body.
So starting from a BAC of 0.08….
After 1 hour – your BAC would be 0.065
After 2 hours – your BAC would be 0.05
After 3 hours – your BAC would be 0.035
After 4 hours – your BAC would be 0.02
After 5 hours – your BAC would be 0.005
Alcohol would be eliminated from the body at about 5 hours and 20 minutes (the body metabolizes alcohol at the rate of about 0.005 per twenty minutes, as 0.005 x 3 = 0.015).
So it is easy to tell when your body will be free of alcohol. It is not so easy to tell, however, what your BAC is if you do not have some kind of alcohol tester, be it a breathalyzer or a disposable alcohol test.
Getting to a BAC of 0.08 is not that difficult. For a 140 lb man, it would be 3 drinks in one hour. If someone is binge drinking, they could get into a situation where alcohol remains in their body for 10 hours or more.
Does drinking coffee help you process alcohol faster or sober up?
No. Only time can sober you up, the time it takes alcohol to metabolize or move thru your body which is about the same for everybody - the rate of about .015 percent of blood alcohol content (BAC) per hour. Many people say black coffee or cold showers help them sober up, but it is not true, the body has to process the alcohol.
How does alcohol effect driving?
This chart shows the Blood Alcohol Level and an approximate number of beers to get you to that BAC and the effect it will have on your driving skills. As you can see it can only take two beers to get you to a .02% BAC which will effect your judgement skills and then three beers can make it difficult to steer a car.
With an alcohol test you can test your BAC as it is processed by your body. Even though you stopped drinking hours ago, the home alcohol test can, like a breathalyzer, detect your steadily dropping BAC.