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 Home Brew Forums > ((og -1) / 4) + 1 = Fg?
01-28-2010, 01:05 AM   #1
Haputanlas
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 ((og -1) / 4) + 1 = Fg?

I was watching a Youtube video about Hydrometers and I was presented with a formula that specifies how you come up with the FG of a beer based on the OG. Is this formula correct? Or is this just a rule of thumb? I would assume that this would be just a rough calculation due to unfermentables that can affect the gravity. I just wanted to know what the general consensus is, or the real answer.

((OG -1) / 4) + 1 = FG?

TIA

Justin

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01-28-2010, 01:10 AM   #2
FlyGuy
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It is just a rule of thumb. It removes 75% of the gravity points associated with the dissolved solids in your beer (i.e. sugars), because most yeast can ferment to around 75% attenuation. But your recipe, brewing process, yeast strain, and fermentation characteristics all affect this number, too.

01-28-2010, 01:11 AM   #3
conpewter
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general rule. Your FG will change depending on the type of brew and how much the yeast attenuate.

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01-28-2010, 01:15 AM   #4
Haputanlas
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Thanks guys,

Conpewter,

I love the avatar pic and quote. I'm a big V for Vendetta fan.

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01-28-2010, 02:57 AM   #5
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I like his quote, but not his avatar. It scares me.
If you ever do find out the formula for predicting FG, I'd love to know what it is.

-a.

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01-28-2010, 03:04 AM   #6
Haputanlas
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Actually, I like your quote even better. I'm a proud computer geek.

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01-28-2010, 01:55 PM   #7
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Quote:
 If you ever do find out the formula for predicting FG, I'd love to know what it is. -a.
The answer is there is no answer, only approximations. There are too many variables. The more variables you control and the better you control them, the narrower the range.
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01-28-2010, 02:14 PM   #8
motobrewer
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your yeast should list its attenuation range.

that's a good place to start.

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