Boil-Off Concerns on a 90min Boil

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

Iowa Brewer

Well-Known Member
Sep 14, 2018
Reaction score
Hi all,
I'm plan to do AHA's Rogue Chocolate Stout clone on Wednesday. My boil setup is two canning kettles on a gas stove. Because I use two kettles I'm worried I'm going to lose more than most during that 90min boil (it works fine with 60min, but this is my first 90min run). The MoreBeer Sparge calculator says I should be fine with 9.39 total gallons on my 12.69-lb grain bill to produce a 5 gal batch. Does that sound realistic? Would it hurt to add an extra half gallon?
As ever, thanks!