OG and FG of beersmith and beer tools pro

[shushikiary]

So I've been copying recipies over from beer tools pro into beer smith and have found that the OG and FG and IBU dont line up.

I setup my equipment in beersmith with what lines up with what I've had in the past brewing with my system (this is all extract brewing by the way)

I've had 2 batches that have exactly matches what beer tools pro put out for the OG and FG, and 2 patches that were off by quite a bit.

The two batches that were off by quite a bit are fair amount closer to what beersmith calculates.

I'm curious, is it normal for the SG and IBU readings of them to not line up? Do I have them setup wrong or something?

Perhaps I'm just comming from a background of specific science that uses exact numbers and expects exact results when this type of science is very not specific and can vary widely because the equations are so imperically based, and it's really bothering me that I'm not matching my numbers exactly...

 

[ajf]

I don't know about BTP, but Beersmith seems to give low extract potential when compared to Promash and the Manufacturers specifications (on those extracts that I have checked). This could affect the OG readings. I wouldn't pay much attention to the FG predictions, as (in Beersmith) they appear to be based solely on the average attenuation of the yeast. There are many other factors that affect the FG, but Beersmith doesn't seem to take them into account.
As for IBU predictions, there are a number of different formulae for calculating IBUs. The most common ones are Garetz, Rager, and Tinseth. They can vary quite widely, and if you have Beersmith is set up to use a different algorithm than BTP, then this will probably explain the IBU differences.

-a.