Beersmith discrepency for IBUs in recipe

[Yourrealdad]

I have looked around the interweb and it seems like this comes up every now and then and usually is user error, so I am probably missing something.

I put in a recipe from Jamil's Brewing Classic Styles, the American Stout to be exact. The recipe calls for a total of 73 IBUs, but when I put it into Beersmith it gives me about 83 IBUs

The IBU formulas are set up to Rager (to match the recipe), the amounts of hops and AA are corrected, the boil volume is the same, so what am I missing?

Should I adjust the recipe in Beersmith until I get Jamil's amount or should I got with the amount recommended by the recipe in the first place?

Thanks

 

[Oginme]

First, check on the settings for the recipe from BCS. Jamil actually produces 6 gallons of wort and transfers 5 to the carboy, so you need to account for this loss.

Second, regardless of the recipe, the calculations for IBU is an estimation only and highly dependent upon your system (surface area, boil rate). Your hop utilization factor may be set different from how Jamil's recipe is calculating it. While this can be adjusted under 'options' >> 'bitterness'. I would recommend making the recipe as you have entered it, and then deciding if you need to adjust the hops up or down depending upon how your first brewing comes out. Once you have this down, you can make changes to future recipes to accommodate your observations.

 

[Yourrealdad]

Yeah I usually end up with a similar volume as Jamil's recipes. I do think that some times my beers are slightly more bitter than I would like, and I think that my water also lends itself towards bitter type beers