From the BrewCipher user guide:
What is BrewCipher?
BrewCipher is a general purpose brewing workbook that is designed in an
integrated way. Instead of several standalone calculators, the tabs in the
BrewCipher workbook share data, which saves the user time.
I developed BrewCipher mainly because none of the other software programs
or spreadsheets predicted attenuation, and thus final gravity, very well. For the
most part, the only variable taken into consideration was yeast strain.
BrewCipher adds mash temperature, mash length, and grain bill to the variables
used to predict attenuation. BrewCipher is not open source, but it is a
collaborative effort. BrewCipher was originally inspired by the work of Mattbk of
the Beer Advocate (BA) homebrewing forum. The attenuation calculation
model uses data published by Greg Doss and Kai Troester. Post-boil hop
additions are modeled based on the work of Mark G. Malowicki. The water
chemistry models were developed by utahbeerdude of the BA forum.
Refractometer conversion calculations are based on the work of Sean Terrill.
BrewCipher continues to evolve, based on ideas suggested by users. Perhaps
best of all, BrewCipher is free.