Mash Efficiency Calculation Issue

I'm sure this is something I'm doing wrong but I can't find the error. I cannot get the mash efficiency number from my last brew to match to the calculation I do by hand. Using the values for each grain and then multiplying by how many pounds in the recipe the max points is 897.75. My pre-boil volume ended up being more than estimated but I entered in the value of 14.1 gallons for measured. That calculates to 63.67 (897.75/14.1) for the max PPG possible at 100%. My gravity was 1.043 and if you take 43/63.67 it comes out to 68% actual mash efficiency. But BeerSmith says my measured mash efficiency was 65.2%.

Where is my math wrong?

Grain Max Points Pounds Max Points
Pale Malt (2 row) 36.00 22 770
Caramel Wheat 35.00 1 34
Munich Malt 37.00 1 36
Victory Malt 34.00 1 33
Peat Smoked Malt 34.00 0.75 24.75
Total 25.75 897.75

100% = extracting everything.

pretzelb said:

Where is my math wrong?

Grain Max Points Pounds Max Points
Pale Malt (2 row) 36.00 22 770 792
Caramel Wheat 35.00 1 34 35
Munich Malt 37.00 1 36 37
Victory Malt 34.00 1 33 34
Peat Smoked Malt 34.00 0.75 24.75 25.5
Total 25.75 897.75 923.5

Click to expand...

923.5/14.1 = 65.49
BeerSmith: 65.5

Actual Efficiency: 65.7%
BeerSmith @ 65.7% = 1.043

Where are you getting the higher point values for each grain? I went back and read several articles on the method to calculate this and all of them said to multiply the amount of grains buy the max points for that grain. The values I got the the grains were what BS had as the max value. If those are not the max value per grain then what are they? IIRC they even closely matched the values in my old book by Palmer.

pretzelb said:

Where are you getting the higher point values for each grain? I went back and read several articles on the method to calculate this and all of them said to multiply the amount of grains buy the max points for that grain. The values I got the the grains were what BS had as the max value. If those are not the max value per grain then what are they? IIRC they even closely matched the values in my old book by Palmer.

Click to expand...

The "Max Points" can reference several values available to the brewer. However, leaving aside how the grain potentials are derived, 100% efficiency always means extracting 100% of the "max points." Your second column is labeled "Max Points," which in brewing language is the resulting gravity (extract potential) of 1 lb mashed to make 1 gallon of wort.

When multiplied by the weight used and then the sum is divided by volume, you get ppg (points per pound per gallon). Your fourth column reduced the sums for some reason, creating the math error for 100% extraction (efficiency).

Well that is embarrassing. I checked the formulas in the spreadsheet and it had something like (max pts -1) * lbs of grain. Why I had the "-1' in there I'll never know. I might have started with something 1.036 and was fooling with the formula and then just switched to "36" and not updated the formula.

pretzelb said:

Why I had the "-1' in there I'll never know.

Click to expand...

Just a guess, but you may have started by using 1.036 and later converted your entry to the more typical 36 without changing your formula.

No big deal. Sometimes I am so perplexed by something that I have to ask a question, only to then see the solution right before my eyes. It's as if the universe needs to remind us all to be humble, once in a while.