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Old 03-25-2009, 06:24 PM   #1
Superdave
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Default How to predict final gravity? Formula?

How do you figure out expected final gravity?

I brewed a couple beers about a week and a half ago. I was just wondering if there was any way to guess what the final expected gravity was.

First batch was an IPA, mashed at 152 deg for 60 min, OG was 1.060, yeast used was Wyeast 1272, American Ale II, attenuation listed at 72-76%. Fermented at 64-65 deg. I pitched a starter made from the yeast in the bottom of a few bottles, so it was a pretty strong pitch. (Quite a bit of sediment by the time it was pitched.)

Second batch was a lager, mashed at 147 or so for 90 min, OG was 1.043, yeast used was Wyeast 2112 (real sure on that), attenuation listed at 67-71%. Fermented around 60 degrees.

Is there some kind of formula to guess what the final gravity will end up being? Thanks!



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Old 03-25-2009, 06:32 PM   #2
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There is no accurate way to calculate FG. It depends on the fermentability of your wort, how much yeast you pitch, how healthy it is, and other factors. Some software will give you an estimate based on the yeast's attenuation rating, but that rating is for comparing one yeast to another rather than an absolute indicator of FG. After you brew the same batch a few times, you can start making a guess.



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Old 03-25-2009, 10:10 PM   #3
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I use and enjoy Beersmith, which will give you gravity estimates. You can download a copy and use it during a free trial period to see if you like it. Cheers,

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Old 03-25-2009, 10:36 PM   #4
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While beersmith does gove etimites it does not account for things like mash temps or fermentation temps or use of non-fermentable malts.

That said it does give you a rough idea.

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