how much alchahol content do I have

I bottled my 3rd batch yesterday, and all I can say is with time and expierience, I am getting better at the carbonating and filling, I would like to find out how much alchahol my beer has ended up with, the OG was 1.040 and it stopped and bottled at 1.010 Is this how I figure the percentage?

(OG - FG) * 131 = ABV In your case it is 3.93%

In the Joy of Home brewing it states OG - FG x 105. Where did you get 135. I am a noob, just wondering.

DerekJ said:

(OG - FG) * 131 = ABV In your case it is 3.93%

Click to expand...

That's the formula that I use too, and it matches up with the online calculator.

Og-fg x 131= alcohol by volume (abv)
Og-fg x 105 = alcohol by weight (abw)

Thanks for clarifying Matt! The only places that I know that use Alcohol by Weight are the 3.2 alcohol states (3.2 alcohol by weight requirement is roughly 4 by volume)

twalte said:

Thanks for clarifying Matt! The only places that I know that use Alcohol by Weight are the 3.2 alcohol states (3.2 alcohol by weight requirement is roughly 4 by volume)

Click to expand...

I think taxes and legal regulations are done by weight, and labeling usually by volume?

There are a number of formulas out there. Most of the quick ones are (OG-FG)*constant. 131 I see a lot. I use 131.25 for estimation purposes.

There's also (OG-FG)/.0075.

The one I use is ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794). This one's supposed to take into account real vs. apparent attenuation, and all those other variables not accounted for in a simpler equation, and supposed to be more accurate at higher gravities. Once you get into the 7% range, the difference is pretty pronounced.

At the end of the day, they're all approximations. The only way to know for sure is to have it physically tested.