Makes me think something is wrong with my process or calculations but I perplexed why different calculators give different #s with the same entry data.

Those spreadsheet calculators operate off of equations that have been fitted to data points collected from various malt samples. The thing is some of these data points are outliers and don't fit well within the fitted equations, also each malt and worse yet, each batch is different. BruNwater most likely has three equations fitted to samples of base, crystal and roast malts. Try setting a base malt as a roast malt and look at the effect it has on the predicted pH.

Other calculators like "Mash Made Easy" allow you to enter what is known as the DI pH of each malt. The DI pH is the pH of a mash made with distilled water and a small amount of a finely ground malt sample.

There is no spreadsheet or set of equations that can fully and accurately predict mash pH, though most do a good approximation. (Of course these spreadsheets *have* done a great service to the homebrew world.)

Certainly data entry errors, measurement errors, accuracy errors and repeatability errors, etc.. all accumulate and affect the outcome.

The best way to determine mash pH is to conduct a test mash. This is a very small proportinally scaled down mash made of the same malts as the original recipe. From this one can determine what has to be done, if anything, to correct the pH.

If you'd like to read more about how the spreadsheets work:

Kai's paper:

http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdfAJ Delanges papers:

http://www.wetnewf.org/untitled.html