If I’m ever in a position where I want to consume many beers (more than 2), I’ve already established driving is completely out.  I have arranged for transportation from a designated driver or mass transit.  I haven’t considered drinking 12 beers since college, and I’m not sure I could even drink 12 back then.  After 6 beers I start losing the horizon.  I can only imagine what prompted someone to perform this search.

Anyways, it sounds like fun so let’s figure out the answer.

How does the breathalyzer work?

Alcohol has two exit paths out of your body, three if you can’t hold your liquor.  You either metabolize the alcohol or you excrete it in some fashion (not counting sickness).  About 5% to 10% of the alcohol you consume exits your body via breath, sweat, and piss.    Since you will breathe out a certain percentage of your pub crawl, you can measure the amount of alcohol exiting your mouth into a breathalyzer.  Once you have measured the amount of alcohol you are breathing out, you can calculate how much alcohol is still in your system.  This is how breathalyzers work.

All alcohol is quicker, not just liquor

If 10% exits the system, simple math states 90% of the alcohol is left in your body.  As you can see from these percentages, peeing often will not really help you.  The reason is your body absorbs alcohol quickly, must faster than food.  Alcohol will take the express route through your stomach and into your blood stream.  About 20% of alcohol consumed is absorbed immediately in an empty stomach.  This alcohol can reach your brain in about a minute.  That’s why a shot will “hit you”.

Breaking down the alcohol

Your liver metabolizes the alcohol using an enzyme.   I won’t geek out on you too much by describing how the enzymes work, but the rate the enzymes can break down the alcohol is dependent on the amount of the enzymes in your body.  If your body contains little amounts of the enzymes it will take longer, however, the amount of enzymes contained in most people does not vary wildly from the average.

The rate your body breaks down the alcohol is a rate of 20 to 30 milligrams of alcohol per deciliter of blood, per hour.  This amount works out to be about 0.015 blood alcohol content (BAC) “points” per hour.

Some people suggest your body breaks down about one drink per hour, but I say it really depends on what you are drinking.  For this exercise, we’ll assume drinks are equal.  In any event, if your BAC is 0.150 it will take 10 hours (0.150 divided by 0.015) before the alcohol is completely out of your system.

How long after 12 beers can you pass a breathalyzer?

From the original question posed, we will assume you drank 12 beers.  It would be dangerous and difficult to consume 12 beers in one hour.  12 beers in one hour could result in death; or just a trip to the emergency room if you are lucky.  We’ll assume you are not pounding the beers, and estimate you are consuming 3 beers an hour.  This would be 12 beers in 4 hours.

If you weigh 170 lbs and you drink 12 beers, your BAC will be around 0.265.  That’s high enough to make you pass out, and be potentially life threatening.  Of course we have to subtract 4 hours of your body excreting and metabolizing the alcohol.  Four hours times 0.015 equals 0.060.  Your resulting BAC will be 0.205.

Starting from this BAC, your body needs almost 14 hours to completely metabolize the alcohol.  Of course to pass the breathalyzer in all 50 states, your BAC needs to be under 0.04.  A 0.04 will not get you a DWI (driving while intoxicated), but you can be charged with a DUI (driving under the influence).  To legally pass the breathalyzer after 12 beers in three hours, you need a little over 11 hours.

I’m in a hurry, can you speed things up?

How can you speed this up, you ask?  You can’t.  The rate of alcohol metabolism is dependent on enzymes breaking down the alcohol.  Coffee, food, exercise, water, or prayer will not accelerate the process.

Consuming food or water while drinking will slow the absorption of alcohol into your blood stream, but it will not change the amount of alcohol your body needs to process.  It is helpful though, since it slows the rate at which the alcohol enters your blood and thus impairs you.