hop partial boil late addition

[pennyloaf]

I was looking at the deception cream stout and was thinking about doing a partial boil (end up with 4 gal so I can add in my gal of cold water from the fridge) and figured I should do a late addition of DME as well.

Using the how to brew book, I can calculate for late addition but unsure of how to calculate for partial boil.

Do I just say boil vol = 4 gal, final vol = 5 gal, AAU = 4/5*(calculated AAU for 4 gal boil)??

 

[RonPopeil]

I consider late additions to be seasoning and disregard IBU's from them. I wouldn't worry about it. Especially true if it's a hoppy beer.