Kegconnection Complete Starter Kit and More Giveaway!


Home Brew Forums > Home Brewing Beer > Beginners Beer Brewing Forum > ((og -1) / 4) + 1 = Fg?

Reply
 
LinkBack Thread Tools
Old 01-28-2010, 12:05 AM   #1
Haputanlas
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jan 2010
Location: Austin, TX
Posts: 2,970
Liked 57 Times on 56 Posts
Likes Given: 38

Default ((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

__________________
Haputanlas is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 12:10 AM   #2
FlyGuy
Feedback Score: 0 reviews
 
FlyGuy's Avatar
Recipes 
 
Join Date: Jan 2007
Location: Calgary, Alberta
Posts: 3,618
Liked 127 Times on 40 Posts
Likes Given: 7

Default

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.

FlyGuy is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 12:11 AM   #3
conpewter
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
conpewter's Avatar
Recipes 
 
Join Date: Nov 2007
Location: East Dundee, Illinois
Posts: 5,106
Liked 40 Times on 35 Posts
Likes Given: 7

Default

general rule. Your FG will change depending on the type of brew and how much the yeast attenuate.

__________________

"People should not be afraid of their governments. Governments should be afraid of their people." - V

Primary: Nothin
Secondary: Shady Lord RIS, Water to Barleywine, Pumpkin wine, burnt mead
Kegged: Crappy infected mild
Bottles: Apfelwein, 999 Barleywine, Oatmeal Stout, Robust Porter, Robust smoked porter, Simcoe Smash

conpewter is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 12:15 AM   #4
Haputanlas
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jan 2010
Location: Austin, TX
Posts: 2,970
Liked 57 Times on 56 Posts
Likes Given: 38

Default

Thanks guys,

Conpewter,

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

__________________
Haputanlas is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 01:57 AM   #5
ajf
Senior Member
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
ajf's Avatar
Recipes 
 
Join Date: Oct 2005
Location: Long Island
Posts: 4,643
Liked 99 Times on 93 Posts
Likes Given: 39

Default

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.

__________________

There are only 10 types of people in this world. Those that understand binary, and those that don't.

ajf is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 02:04 AM   #6
Haputanlas
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jan 2010
Location: Austin, TX
Posts: 2,970
Liked 57 Times on 56 Posts
Likes Given: 38

Default

Actually, I like your quote even better. I'm a proud computer geek.

__________________
Haputanlas is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 12:55 PM   #7
david_42
Feedback Score: 0 reviews
 
david_42's Avatar
Recipes 
 
Join Date: Oct 2005
Location: Willamina & Oak Grove, Oregon, USA
Posts: 25,651
Liked 133 Times on 126 Posts

Default

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.
__________________

Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

"I would like to die on Mars, just not on impact." Elon Musk

david_42 is offline
 
Reply With Quote Quick reply to this message
Old 01-28-2010, 01:14 PM   #8
motobrewer
I'm no atheist scientist, but...
HBT_SUPPORTER.png
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2009
Location: Thiensville, Wisconsin
Posts: 6,600
Liked 207 Times on 182 Posts
Likes Given: 366

Default

your yeast should list its attenuation range.

that's a good place to start.

__________________
motobrewer is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools