How do I determine the ABV% of my home brew beer?

Question

How do I determine the ABV% of my home brew beer?

Answer 1

There's a little glass instrument, forget what it's called and you put a few drops of still beer then turn it upside down. As gravity drops the drop it levels off at the ABV. Not completely accurate but close.

Also worked with wine. Supply stores will know!

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Answer 2

If you don't have a hydrometer, which measures the gravities, then you would've never had the original gravity.

You could use more cruder methods of measuring the alcohol content, to get you in the ballpark.  If you have an accurate scale and volumetric measuring device you could figure out the overall density.  Given water is 1g/mL, and alcohol is 0.789g/mL, you could then find out what %ABV the beer is.  (If you want to skip the math, then %ABV = ( 1 - total density) / 0.211 ).

Of course, if you really wanted to know, you could sacrifice a beer.  First measure the volume of beer precisely.  Then bring it up to 174F and let it stay there for a couple minutes.  Pour it all back into the measuring device and see what you lost.  The %ABV is just the amount lost / original volume.  Don't wash the measuring device while you dealcoholize the beer.

Answer 3

As long as you took measurements along the way, the best way to determine ABV is as follows:

OG (Original Gravity) - FG (Final Gravity) x 129 = approximate alcohol by volume (ABV)

It's important, of course that you took gravity readings along the way.  Also, you need to make sure that your gravity readings were corrected for temperature.  

If you're not a science guy, you can approximate with one reading.  Generally, this can vary based on yeast strain and sugar content, your alcohol level will be around 10% of your OG.  So, if your OG is 1.062.  Your final gravity should be around 6.2%.

Answer 4

What you need is a hydrometer.  It is a glass tube that floats in your beer. It floats higher or lower in the wort depending on the density  of the liquid.  The more sugar dissolved, the denser the liquid.  More sugar means more alcohol.

You measure the density (gravity) of the liquid, before (Original Gravity), and after fermentation (Final Gravity), take those numbers, and use them to figure out the amount of sugar that has been fermented into alcohol.  I use an online calculator designed for the purpose.  Just plug in the gravities into http://www.beertribe.com/gizmos/calcs/ab... and it will tell you approximately how much alcohol is in there.

Your numbers aren't going to be exact, but they will be "good enough".  Priming sugar will also add a little bit of alcohol, but not very much.