Simple subtraction. Take a hydrometer reading right before you pitch the yeast into your wort (see “How do I take a hydrometer reading?” in FAQs). Make a note of this reading, which should be in the range between 1.040 and 1.080, depending on the recipe and style you are brewing.
After the fermentation is complete, take another hydrometer reading right before you bottle. Be sure you take your reading BEFORE you add the priming sugar, as this will skew the reading. This reading will usually fall between 1.010 and 1.030, again depending on the recipe and style.
Then you simply subtract the second reading from the first, and consult a conversion chart (such as the one found in “The Brewmaster’s Bible”, or many other homebrewing books) to determine the alcohol content.
Let’s say that your starting gravity was 1.042, and your terminal gravity was 1.010. This makes a difference of 0.32. Looking this up in the conversion chart will tell you that your brew is 4.1% A.B.V. (alcohol by volume).Products related to this FAQ
