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Old 04-26-2007, 04:30 AM   #1
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Default OG -> FG = ABV Math

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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Old 04-26-2007, 04:32 AM   #2
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Og - Fg * 131
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Old 04-26-2007, 04:36 AM   #3
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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?
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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%
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Old 04-26-2007, 04:39 AM   #4
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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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Old 04-26-2007, 04:44 AM   #5
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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
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Planning - a 40th Birthday Lager for Sept 09 (Start October 08

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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%
Drinking - Brewhouse Pale Ale ABV 5.2%
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Old 04-26-2007, 05:03 AM   #6
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Funny, TCJOHB, 3rd ed, page 43 says:

OG - FG * 105 = ABW

ABW * 1.25 = ABV

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Old 04-26-2007, 05:10 AM   #7
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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.

You're just "showing your work."
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Old 04-26-2007, 05:19 AM   #8
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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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Old 04-26-2007, 05:25 AM   #9
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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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Old 04-26-2007, 04:52 PM   #10
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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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