Alcohol Calculations

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Shambolic

Well-Known Member
I know this doesn't matter to some people, but for those who do bother:

What formula do you use for calculating the alcohol content of your brews? The basic intro. book I first got said (OG - FG)*14. Another source says (OG - FG)*13.4. Online calculators all seem to give different answers.

Has anyone ever had a brew lab tested?

david_42

Well-Known Member
Either calculation will get you close, but if you really want to know:
http://www.stpats.com/testeq.htm#vinometer

Ebulliometer \$445 [SIZE=-1]
[/SIZE]Now with Longer 10" Thermometer/Scale for greater precision.[SIZE=-1]
Precision % alcohol determination.
Accurate up to 1000 meter (3300 ft) elevation.
Accepted by Treasury Dept. Nearly as precise as distillation but much easier. Brass. Padded attache case included. Alcohol burner included. Method based on boiling point difference between pure water and wine. Two step process--first use distilled water to set zero point, then boil wine. Thermometer scale reads % alcohol directly. [/SIZE][SIZE=-1]
Note on sweet wines. Sugar will cause error in reading. Therefore, sweet wines should be diluted for accurate readings.

Or take exactly 100 cc of your ale at 20C and heat it at 83C until all of the alcohol has boiled off. Then cool back to 20C and measure the volume again. The difference is ABV.
[/SIZE]

Nwcw2001

Well-Known Member
Abw= (og-fg) * 105 Abv= Abw*1.25

Nwcw2001

Well-Known Member
my tripple: (1.096-1.012)*105=8.82 ABW 8.82*1.25=11.025ABV

casebrew

Well-Known Member
Don't all hydrometers have an alcohol scale on them? But thanks for the math, Nwcw (Mind I use your first name?)

Nwcw2001

Well-Known Member
no only close friends call me NWCW. everyone else calls me John!!!! lol

Mike's Brew and Brat

Well-Known Member
Got this from Northern Brewer Hombrew Forum.
"For ABW take your OG and subtract your FG then multiply by 105. An example would be OG 1.048 minus FG 1.010 =0.038 X 105=3.99% to convert to ABV multiply that by 1.25 For example using the 3.99 X 1.25=4.98&#8230; 5%
Or to go right to ABV multiply your OG-FG by 131, same thing."

I have found this on some other websites as well.

rewster451

Well-Known Member
HB Bill gave me this formula and I think it's as close as you can get without being totally anal:

OG-FGx129=ABV

It's what I use now.

usmcruz

Banned
Sounds like its being made more difficult than it has to be. Get a hydrometer with a potential alcohol scale on it and subtract the OG potential alcohol from the FG potential alcohol, and that number you get will be the alcohol content. your done

homebrewer_99

Well-Known Member
rewster451 said:
HB Bill gave me this formula and I think it's as close as you can get without being totally anal:

OG-FGx129=ABV

It's what I use now.
True, but I've also seen calculations as low as 125 and as high as 131. I read 129 elsewhere, so I use 129 since it's between those numbers and probably more correct.

However, in Charlie P's books (1st and 3rd editions) it's OG - FG X 105 = ABW. To convert ABW to ABV take ABW X 1.25, and to convert ABV to ABW multiply by 0.80. I know in a lot of these places we drop the decimal, but we know where it's supposed to go in the final number.

In the Brewer's Bible it's also 125.

129 was easy to remember because it's a odd number, but 125 will make calculations easier. I can change my calculations and go with the majority no big deal.

Blaine

Well-Known Member
Shambolic said:
I know this doesn't matter to some people, but for those who do bother:

What formula do you use for calculating the alcohol content of your brews? The basic intro. book I first got said (OG - FG)*14. Another source says (OG - FG)*13.4. Online calculators all seem to give different answers.

Has anyone ever had a brew lab tested?
Formula is quite Simple

Og-Fg/7.46 + 0.5 ( allow the .5 for priming sugar )

eg 1035-1006/7.46+.05= 4.38 %

homebrewer_99

Well-Known Member
Interesting. I never saw that one before.

It's funny how something that should be so certain has so many ways to get there.

I would think there would be only one way to perform the CORRECT calculation.