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Estimated Gravity and Top Up water


New Forum Member
Dec 17, 2018
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I am brewing larger batches than my boil kettle can hold therefore I am adding top-up water to the fermenter when I transfer the wart.
I am noticing that although the estimated gravity figures for pre-boil and og are always spot on (its magic!) the expected post-boil gravity is showing the figure for the OG.

for example, I have a 54L batch here where I will be using 20L top-up.
the expected pre-boil gravity is 49.9 Litres @ 1.063
but expected post-boil gravity is 38.54 Litres @ 1.055

it would be nice if this figure was accurate to the stage rather than to the OG after the 20L of top-up is added.

Am I missing something?

Thanks in advance.



Grandmaster Brewer
Mar 16, 2013
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New Hampshire, US
Since OG is technically the gravity in the fermenter, that is what the program is giving you.  I agree that with top off being a part of some brewer's regular practice, that it would be good to have a post boil gravity target as well.  Brad made the adjustment with the post mash versus pre-boil gravity so that people who add extract or other sugars could get an honest target for what they should expect out of the mash tun.  It would make sense to do the same on the tail end of the process.