All Grain BIAB calculation question

[brewzofo1]

I am getting ready to brew an IPA. I've looked all over here and other places for amount of water to boil for all grain BIAB (no sparge). I have 12.5 lbs of grain, 4oz of hops to make a 5 gallon batch at 60 minute boil. I will be brewing outside in my garage. Todays temp will be around 65F. From my calculatons and looking around this site and others I should start off with 8 gallons of water for my mash to get a 5 gallon batch. Is this about right?

 

[Kaz]

Without running any calculations myself, I will say that most of my average gravity brews start off with about 8 gallons, so I think you are in the ballpark.