OG -> FG = ABV Math - Home Brew Forums

 Home Brew Forums > OG -> FG = ABV Math

04-26-2007, 04:30 AM   #1
sAvAgE
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Jan 2007
Spruce Grove Alberta
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I know if I actually surfed I could find it. If you understood What I did for work and had the day I did you would do the same thing. I DO SEARCH. Just not tonight

What is the Math equation you all use to calculate OG from FG to give you your ABV?

Thanks all for not giving me any heat over this. I am just tired
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Bottled - Honey ApfelMead 02/23/08 ABV 10.0%
Bottled - Oktoberfest 5.2%
Bottled - Candian Light Lager 4.85
Bottled - Munich Dark Lager 5.6%

Drinking - Apfelwein FG 2/29/08 ABV 8.5%
Drinking - Brewhouse Cream Ale ABV 4.7%
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04-26-2007, 04:32 AM   #2
Desert_Sky

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Mar 2006
Sierra Vista, AZ
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Og - Fg * 131

04-26-2007, 04:36 AM   #3
sAvAgE
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Jan 2007
Spruce Grove Alberta
Posts: 284
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Quote:
 Originally Posted by Chimone Og - Fg * 131
Dont think that is right

here is what I get

OG is 1041
FG is 1001

then if I multiply by 131 I get 5,240 so ABV is 5.24? is that correct?
__________________
Planning - a 40th Birthday Lager for Sept 09 (Start October 08

Next Up - First All Grain 40th birthday lager

Primary -

Secondary -
Secondary -

Bottled - Honey ApfelMead 02/23/08 ABV 10.0%
Bottled - Oktoberfest 5.2%
Bottled - Candian Light Lager 4.85
Bottled - Munich Dark Lager 5.6%

Drinking - Apfelwein FG 2/29/08 ABV 8.5%
Drinking - Brewhouse Cream Ale ABV 4.7%
Drinking - Brewhouse Pale Ale ABV 5.2%

04-26-2007, 04:39 AM   #4
Yuri_Rage
Gritty.

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Jul 2006
Southwest
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Quote:
 Originally Posted by sAvAgE Dont think that is right here is what I get OG is 1041 FG is 1001 then if I multiply by 131 I get 5,240 so ABV is 5.24? is that correct?
That's exactly right. You just need to remember where the decimal goes:

1.041 - 1.001 = 0.040
0.040 * 131 = 5.24%
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04-26-2007, 04:44 AM   #5
sAvAgE
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Jan 2007
Spruce Grove Alberta
Posts: 284
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Quote:
 Originally Posted by Yuri_Rage That's exactly right. You just need to remember where the decimal goes: 1.041 - 1.001 = 0.040 0.040 * 131 = 5.24%
OK Great thanks Guys. Cheers to you all
__________________
Planning - a 40th Birthday Lager for Sept 09 (Start October 08

Next Up - First All Grain 40th birthday lager

Primary -

Secondary -
Secondary -

Bottled - Honey ApfelMead 02/23/08 ABV 10.0%
Bottled - Oktoberfest 5.2%
Bottled - Candian Light Lager 4.85
Bottled - Munich Dark Lager 5.6%

Drinking - Apfelwein FG 2/29/08 ABV 8.5%
Drinking - Brewhouse Cream Ale ABV 4.7%
Drinking - Brewhouse Pale Ale ABV 5.2%

04-26-2007, 05:03 AM   #6
homebrewer_99

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Feb 2005
Atkinson (near the Quad Cities), IL
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Funny, TCJOHB, 3rd ed, page 43 says:

OG - FG * 105 = ABW

ABW * 1.25 = ABV

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04-26-2007, 05:10 AM   #7
Yuri_Rage
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Quote:
 Originally Posted by homebrewer_99 Funny, TCJOHB, 3rd ed, page 43 says: OG - FG * 105 = ABW ABW * 1.25 = ABV
Funny...

105 * 1.25 = 131.25.

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04-26-2007, 05:19 AM   #8
homebrewer_99

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Quote:
 Originally Posted by Yuri_Rage Funny... 105 * 1.25 = 131.25. You're just "showing your work."
OK, you're missing it...

Let's say:

OG = 1.055
FG = 1.012
difference = .043

.043 * 105 = 4.515% ABW

4.515 * 1.25 = 5.64% ABV

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04-26-2007, 05:25 AM   #9
Yuri_Rage
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No...you're adding a step to a simple calculation (unless I'm missing a joke here...).

The formula you're using can be simplified to:
((OG - FG) * 105) * 1.25 = ABV

Therefore:
(OG - FG) * 131.25 = ABV

So:
0.043 * 131.25 = 5.64% ABV
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04-26-2007, 04:52 PM   #10
homebrewer_99

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Quote:
 Originally Posted by Yuri_Rage No...you're adding a step to a simple calculation (unless I'm missing a joke here...). The formula you're using can be simplified to: ((OG - FG) * 105) * 1.25 = ABV Therefore: (OG - FG) * 131.25 = ABV So: 0.043 * 131.25 = 5.64% ABV
I think the only step I'm adding is the one to get ABW.
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