Mash profiles and estimated ABV

I have tried to find some information regarding how BeerSmith 2 calculates the estimated ABV. I looked at the one of the sample recipes (Burton Ale) and first changed the mash profile to Temperature Mash, 2 Step, Full Body which provided an estimated ABV of 5.7%. Then I tried the Temperature Mash, 2 Step, Light Body and got 6.3%.

Everything in order so far My question relates to if I would like to create completely new mash profile. Does BeerSmith 2 actually analyze the different temperatures and times I use in my mash profile to calculate estimated ABV (or is this just for the predefined ones)? If yes, is there any information available of the algorithms BeerSmith 2 use?

/Seven Brewers

Two things:

Beersmith uses the mash profile to estimate your final gravity.  It uses a linear approximation of mash-temp vs. ferment-ability.  You can enable/disable this or modify it on the options advanced page.  it is a simple formula and will not be able to adequately take into account the effects of a complex mash profile.  it works reasonably well for a simple single sach-rest based profile.  But, if you do separate beta, alpha, and/or limit-dextrinase rests to maximize fermentability...the fomula may not be able to predict your actual FG.

Second, beersmith calculates ABV between OG and FG.  See these posts from Brad for the formula that BS2 uses. 

http://beersmith.com/blog/2010/09/07/apparent-and-real-attenuation-for-beer-brewers-part-1/
http://beersmith.com/blog/2010/09/14/apparent-and-real-attenuation-for-beer-brewers-part-2/

What they amount to is:

Real_extract = 0.188 * OG + 0.8192 * FG
Attenuation_in_% = 100 * (OG – Real_extract)/(OG – 1.0)

Sorry forgot the final piece:

ABW = (OG-Real_extract)/(2.0665-.010665*Real_extract)
ABV = ABW / 0.788