Calculating HBUs

While I decide whether or not to teach a homebrewing class, I thought I would put some things together that I could use in the class. These will come in no particular order and follow no particular rhyme or reason for when I post. I just felt like it.

Some recipes don't specify hop varieties, mainly because the alpha acid content is hops can vary. Instead these recipes call for HBUs or Home Bittering Units. The final recipe will usually have a IBU (International Bitterness Unit) rating to indicate what the final bitterness of the beer will be. If you brew to style, these figures are vital!

HBUs are calculated by multiplying the AAU (Alpha Acid Unit) of a hop by the number ounces being used. So a pilsner recipe, for example, can have a listing for hops like this:

6 HBU for 60 minutes
10.5 HBUs for 30 minutes
3 HBUs for 10 minutes

If you only have one type of hop on hand, you can still brew to style if you know the AAU of your hops. All you have to do is plug the known values into the equation to solve for the unknown values.

But I'm a visual guy, not a mathematician. So I created a little chart to help me solve the formula.

With this chart, I can visually see that across the bottom you should multiply, and to find the values on the bottom, divide the top value by the opposite bottom value. So, if I have Saaz hops on hand with an AAU of 3%, I would use 2 ounces of Saaz for 60 minutes, 3.5 ounces for 30, and 1 ounce for 10 in the above example.