One more question tomsawyer, how did you calculate the gravity from ppg?
I know the ppg of grain, and I figure 75% efficiency. So instead of 36ppg I use 27ppg (what I'll actually get from mashing). I multiply the ppg by the pounds of grain to get total points. Then I divide total points by gallons of volume.
For example, 3lb malt x 27ppg = 81points / 5gal = 16ppg. So mashing 3lb of malt and adding it to your sparge would add 16ppg to what you alredy have.
Or do you mean ppg vs OG? OG is just 1.0 and then put your ppg number after that.