Estimated Attenuation - are calculations off?

Beersmith 2.3.12

This is driving me crazy.

I made a test recipe and set the weight units to pounds and the volume units to fluid ounces.
I added malt and set the batch size and brewhouse effeciency.
I also set the precision to 10 digits and disabled the Adjust FG for Mash temperture.

Now Beersmith calculates the Estimated OG correctly - no problem there: 1.083680923100

I then add a yeast and sets the yeast min and max attenuation to 50%.

Beersmith now calculates a Estimated FG correctly to: 1.04184046155

This does give an apparent attenuation of 50% using the formula: Apparent_Attenuation_in_% = 100 * (OG-FG)/(OG-1.0)

But Beersmith Estimated attenuation field reads 48,0??

I don't get it. Is it a bug or am I missing something here?


(The Measured Attenuation field also reads 48,0% when entering the OG and FG in the measured OG and FG fields).

Brad?? Did you look at this? I need to understand this.

Maybe this was lost in the pile of posts, but is there an explanation?

Timpervo,

In trying to understand what is going on there is more information required:  (1) Grain bill?, (2) mash temperature?, (3) yeast used?  If you export the recipe as a .bsmx file and post it we can play with it to see if there is something else we are missing.

On a side note, grain potentials are calculated or given to 3 decimal places.  Any calculated figures for specific gravity using these values beyond the thousandths place are really just noise and make it harder to interpret.

timpervo said:

Maybe this was lost in the pile of posts, but is there an explanation?

Click to expand...

BeerSmith assigns a default attenuation level before you add yeast to the recipe. Once the yeast is added, the calculation is based on the max attenuation. If you change that, the FG will follow.

You?ll need to make sure that your yeast dates, viability and pitching rates are correct.

Attenuation is further modified by mash temperature and slope. You can modify the ferment ability slope in the global settings. Of course, a higher mash temperature results in reduced fermentability and BeerSmith accounts for this.

As Oginme pointed out, you?ll need to post an export .bsmx file for us to give you a more detailed answer.