• Welcome to the new forum! We upgraded our forum software with a host of new boards, capabilities and features. It is also more secure.
    Jump in and join the conversation! You can learn more about the upgrade and new features here.

How BeerSmith calculates recipe SRM

dennydeaton

Apprentice
Joined
Dec 7, 2011
Messages
5
Reaction score
0
Hi,

I've read through the related posts on this forum (and others).  I also saw the related BeerSmith blog from 2008. But still haven't found a clear answer as to how BeerSmith calculates the total SRM for a recipe.  I know it uses Morey's Formula, but I'm unsure of the exact MCU calculation it inputs and how it derives that from the grain data.  I want a better understanding of how this works.

Here is a simple example that I went through and calculated it manually. I also ran the same ingredients through BeerSmith but the results are not matching up.  Could anyone tell me the discrepancy?

volume (post-boil): 7.02
grain1: 5lbs @ 2.0SRM (American 2-row)
grain2: 2lbs @ 23.0SRM (Biscuit Malt)

For reference: SRM = 1.4922 [(MCU) ^ 0.6859]

1.4922 * ((5*2)/volume) ^ 0.6859) = 1.90206086681
1.4922 * ((2*23)/volume) 0.6959) = 5.5204466145

1.90206086681 + 5.5204466145 = 7.42 SRM

Beersmith calculates the same ingredients at 6.4 SRM
 
Hi,
  You need to total the MCU up first - so add 5*2 + 2*23 = 56 and then you apply the equation and you will get about 6.3 if my hand calculator is correct.

Brad
 
Thank you for the reply.  That was helpful.

I checked the BYOCalc spreadsheet (http://www.byo.com/stories/article/indices/28-computer-brewing/1690-write-your-own-brewing-spreadsheet) as well, which calculated it like I had originally.  I certainly don't doubt your research, but I'm trying to determine which way is correct.

What caused you to compile the (Weight/SRM) for each ingredient and add them up before running them through Morey's Formula?
 
I tell you what - I will contact Dan Morey himself via email and see what he has to say!

Brad
 
Perfect!  Thanks, Brad.

I've spent more time looking at the numbers and it seems like your method is best, as it is truer the curve-fitting.
 
Hi,
  I got a message back from Dan Morey (author of the Morey equation) and he confirmed that my method is the correct one.  You total up the MCU contributions from the grains before applying the Morey equation.

Brad
 
Back
Top