I can't seem to match my Brewhouse Efficiency from Beersmith with the one I calculate manually. Does Beersmith only use the grain bill, measured OG, and batch volume (volume in the fermenter) to calculate Brewhouse Efficiency? Or is there something else built into the equation?

Here is my grain bill (using information from

http://www.beersmith.com/grain-list/):

5 lbs of US 2-Row (Potential SG: 1.036) = 180 points

0.3125 lbs of Caramel 60 (Potential SG: 1.034) = 10.625 points

0.3125 lbs of Amber Malt (Potential SG: 1.035) = 10.9375 points

0.25 lbs of US Chocolate Malt (Potential SG: 1.028) =7 points

0.0625 lbs of US Roasted Barely (Potential SG: 1.025) = 1.5625 points

0.25 lbs Dark Brown Sugar (Potential SG: 1.046) = 11.5 points

So there is a total of 221.625 potential points. My batch volume of 2.4 Gallons had a measured OG of 1.064.

64 / (221.625/2.4) = 0.693

This gives me a calculated Brewhouse Efficiency of 69.3%. Beersmith gives me a Brewhouse Efficiency of 67.2%. I know it is only off by a couple percentage points, but I would like the math to work out. Also, if Brewhouse Efficiency is what is used to back into a grain bill, I want to make sure I understand how it is calculated.

Cheers,

Chris