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View Full Version : Calculation Formulae (SG, %ABV,...)



JamesP
09-02-2004, 05:45 AM
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/CalcInfo/HydSugAl.htm )

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


Any other handy formulae out there?

WikdWaze
09-02-2004, 03:38 PM
POTENTIAL ALCOHOL from SG

(This allows for FG < 1.000 - see Ben Rotter's site http://members.tripod.com/~BRotter/CalcInfo/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)] ?

ScottS
09-02-2004, 06:59 PM
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. ;D

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?

WikdWaze
09-03-2004, 03:24 AM
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. ;D

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 :-[

JamesP
09-05-2004, 05:33 AM
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

Oskaar
09-05-2004, 11:27 AM
Nice references James! :)

Good information!

Oskaar

jab
09-07-2004, 06:30 AM
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.



<?

function figureAlcohol($ograv, $fgrav, $pmode = 'vol')
{
$alc = (($ograv - $fgrav) * 105);

if ($pmode == 'vol')
{
$alc *= 1.25;
}

return $alc;
}

?>


Hope that helps someone.

-jb

vinoblanco
09-16-2004, 12:14 AM
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