A Beginner’s Guide to Homebrewing: An Introduction to the Art

Part 2: Want to Know the Alcohol Percentage of Your Beer?

So, you’ve made your first extract brew, and your feeling pretty cocky. Your buddies sampled your wares, and so far there are zero casualties. In fact, it’s good beer. No, Great beer. I know what you’re thinking…. “It’s time to call my boss and tell him to shove it, because I’m going to open a brewery!”

Well believe it or not, short stuff, you’ve got a few more things to learn before you file that business license and decide on what soundtrack to blast while you finally take vengeance on the copy machine at work, Office Space Style.  Not to fret though, I’ve got your back. I’m here to enlighten you on another very important aspect of brewing, as well as a good diagnostic tool for monitoring your fermentation. Of course I’m talking about measuring your Alcohol Percentage By Volume.

Testing your ABV is important if you want to know the alcohol percentage in your finished beer, or if you want to see whether the fermentation of your beer is complete.

What You Need To Buy

• A Hydrometer

Here’s a Hydrometer for 11 bucks!

• A Hydrometer Test Jar

Here’s a Hydrometer Test Jar for 5 Bucks!

Instructions for Determining Your ABV with a Hydrometer:

1. Brew your batch of beer as you normally would but don’t pitch your yeast just yet.
2. Immediately prior to pitching your yeast take a sample of your unfermented beer. (Enough to mostly fill your Hydrometer Test Jar)
3. Slowly insert the Hydrometer into the Test Jar weighted end down, and let the Hydrometer float freely.
4. Write down where the liquid level came up to on the Hydrometer. The Reading should look something like: 1.070 or 1.055. This is called your ORIGINAL GRAVITY (OG)
   1. What you are measuring is how much sugar is dissolved into the liquid as compared to regular water. Dissolved sugars make liquid more dense. The hydrometer will not sink as far into liquid that is denser with dissolved sugars, thus making the hydrometer reading (Gravity) higher.
   2. As the yeast eats the sugar in your beer, it replaces that sugar with alcohol, making the liquid less dense, and in turn your Gravity reading lower.
5. Take another reading a few days into fermentation, (to make sure the fermentation is happening)
   1. The number will decrease as fermentation progresses.
      1. EX. If your original reading was  1.065 it should steadily drop. a few days later it will read something like 1.030 and continue dropping from there.
   2. You will know your fermentation is complete when the reading stays the same when you check it 2-3 days apart
6. Once your fermentation is finished (right before you bottle and BEFORE you add priming sugar!) take one last reading on your hydrometer. This is called your FINAL GRAVITY or finished gravity. (FG)
7. I hope you passed seventh grade math because you’ll have to plug your OG and FG into one of the following Alcohol By Volume (ABV) formulas: (the easiest one is #2)

#1.       ABV= * (FG/0.794)

For example: You have an OG 1.075 and a FG 1.020

                    ABV= {76.08 *(1.075-1.020) / (1.775-1.075)} * (1.020/0.794)

                    ABV= {76.08 *(0.055) / (0.7)} * (1.028463476)

                    ABV= {4.1844 / 0.7} * (1.028463476)

                    ABV= 5.97771429  *  1.028463476

                    ABV= 7.68

You would have a 7.68%  ABV Beer.

                 (P.S. Dont round your numbers until the end!)

If that gives you a Huge headache then try this one:

#2.                ABV= (OG-FG) * 131.25
(It’s a little less accurate but much easier)

For example: You have an OG 1.075 and a FG 1.020

                           ABV= (1.075-1.020) *131.25
                           ABV= 0.055 * 131.25
                           ABV= 7.22

                  You would have a 7.22% ABV Beer.

Notice that the difference between the simple math version and the more complex formula is less than half a percent ABV.   7.68-7.22= 0.46

So there you have it. Now you say things like  ”Slow down there, Chief. This one’s 8.6 percent!”