Is it just me Or.....

[Piotrsko]

Long time lurker, newish member.

Can't find the box in the IBU bitterness calculator for dry hopping which is what I do almost exclusively since I'm not a hop bomb fan, prefer mostly British brown ale, irish reds, and stouts but don't care for Guinness.

 

[Mark Farrall]

It's not just you. That calculator looks to be based a more theoretical approach to IBU calculation. Textbook definition of IBUs is (was?) the amount of isomerised alpha acids. The amount of those you get during the dry hop is essentially none (I think about one IBU of alpha acid molecules gets isomerised every week or so at dry hop temps). So people would say there are no IBUs added by dry hopping, which is reasonable based on that textbook definition.

And it does say that it's only calculating boil IBUs, so you'd need to use the full recipe calculator to get something that allows you to set some IBUs for your dry hop additions.

So where the textbook definition suffers is that the standard IBU test returns the amount of materials that are visible in a certain spectrum. This includes more than just iso-alpha acids. And with this test you definitely get an increase (or in some peverse scenarios a decrease) in IBUs when you dry hop. So it's reasonable to include dry hop additions in your recipe.

And then there's the rabbit hole of perceived bitterness ...