Decoction Calculator


Trial Member
Sep 22, 2012
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Suppose I want to do a single decoction mash, with a protein rest at 140F. Does Brewer's Friend have a caculator that will tell you how much mash to take out and decoct to get the mash to 151F when the decoction is re-introduced back into the mash?
At this time we don't have a decoction calculator.

It is something we can look into supporting down the road.
I'm using Brewers friend for the first time, I'm brewing tomorrow. I'm making a NEIPA and like to use a decoction to mash out. It thins out a thick mash from the oats and decreases the possibility of a stuck sparge. I'm bummed Brewers friend doesn't have a decoction calculator. I was using brew toads calculator but it's no more. I'm having trouble finding one.
Second. The equation is rather easy:

decoction volume = total mash volume * (target temp - start temp) / (boil temp - start temp)

Plus 15% - 20%. It works for both fahrenheit and celsius.
It's the mass and temperature that matters. If you can manage to weigh what you pull out of the mash, you can do a simple calculation to get you there using this: or something similar. Just have to use weight instead of volume, though there may not be a lot of difference in the weight/volume ratio of wet grain and water.

For example if you have 10 lbs of grain at 1.5 qts/lb the combined weight of water and grain would be about 41 lbs. In the calculator I referenced, you can fill in the current mash temp and decoction temp (212?), target mash temp and the total weight and it'll calculate the weight of mash/grain you need to pull out.
Like this: