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Thread: Calculation Formulae (SG, %ABV,...)

  1. #1
    Join Date
    Dec 2003
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    Brisbane Australia
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    654

    Default Calculation Formulae (SG, %ABV,...)

    From somewhere else in the Forum

    SPECIFIC GRAVITY from HONEY quantity

    SG = 1 + [ (lbs x 45) / (gals x 1000) ]

    (and for metric people)

    SG = 1 + [ (Kg) / (Ltr x 2.6596) ]

    POTENTIAL ALCOHOL from SG

    (This allows for FG < 1.000 - see Ben Rotter's site http://members.tripod.com/~BRotter/C...o/HydSugAl.htm )

    %ABV = 0.944 + 129.8 x (SG - 1)


    Any other handy formulae out there?

  2. #2

    Default Re: Calculation Formulae (SG, %ABV,...)

    Quote Originally Posted by JamesP

    POTENTIAL ALCOHOL from SG

    (This allows for FG < 1.000 - see Ben Rotter's site http://members.tripod.com/~BRotter/C...o/HydSugAl.htm )

    %ABV = 0.944 + 129.8 x (SG - 1)


    Any other handy formulae out there?
    Would I be correct in assuming that should be
    %ABV = 0.944 + [129.8 x (SG-1)] ?

  3. Default Re: Calculation Formulae (SG, %ABV,...)

    My rule of thumb is 1 lb of honey in 5 gals of water = 0.008 SG = 1% ABV fermented out. Simple, pretty close to reality, and much easier to remember than those equations.

    I have a question about that SG to ABV formula. If I plug in a SG of 1 (= water), I get a ABV% of .994%. What gives?

  4. #4

    Default Re: Calculation Formulae (SG, %ABV,...)

    Quote Originally Posted by ScottS
    My rule of thumb is 1 lb of honey in 5 gals of water = 0.008 SG = 1% ABV fermented out. Simple, pretty close to reality, and much easier to remember than those equations.

    I have a question about that SG to ABV formula. If I plug in a SG of 1 (= water), I get a ABV% of .994%. What gives?
    I guess that's what happens when you use a simplified equation to get an approximation. On the "Mead Made complicated" site they give the actual equations to figure this out, those equations frighten and confuse me

  5. #5
    Join Date
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    Default Re: Calculation Formulae (SG, %ABV,...)

    WikdWaze,

    The brackets were left out because I assumed muiltiplication has precedence over addition
    Goes to show what assuming does.

    Scott S,

    Plugging in SG=1.000 says that your FG=1.000, and your mead isn't totally dry, but still has 0.944% Alc to ferment out.
    When your FG=0.9927 you will have a totally dry mead. Again this is another assumption, because EC-1118 can probably ferment to FG=0.9927, but some of the other yeasts may not. However, we are talking about potential alcohol

    I'm sure you didn't start with OG=1.000

    The URL I mentioned has more details, and there are 5 formulae listed there, each with slightly different results.

    -=-=-=-

    1lb in 5 gal making 1% ABV - that is an easy one to remember, except for the "metric" people :-/

    that makes it (roughly) 0.4 Kg in 19 Litres per 1% ABV

  6. #6
    Join Date
    Dec 2004
    Location
    The OC
    Posts
    7,874

    Default Re: Calculation Formulae (SG, %ABV,...)

    Nice references James!

    Good information!

    Oskaar
    Is it tasty . . . precious?

  7. Default Re: Calculation Formulae (SG, %ABV,...)

    I started writing a PHP application a while back that would allow me to track my brews. Life got in the way and I didn't get very far on it, however, this is the function I was using to figure alcohol content either by weight or vol.

    Code:
    <?
    
    function figureAlcohol($ograv, $fgrav, $pmode = 'vol')
    {
     $alc = (($ograv - $fgrav) * 105);
    
     if ($pmode == 'vol')
     {
      $alc *= 1.25;
     }
    
     return $alc;
    }
    
    ?>
    Hope that helps someone.

    -jb

  8. #8
    vinoblanco Gotmead Visitor

    Default Re: Calculation Formulae (SG, %ABV,...)

    I developed a little spreadsheet that helps you formulate simple recipes, if anybody's interested. Just PM me with your e-mail and I'll send it to you.

    B

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