# Percent alcohol?

### Help Support Homebrew Talk:

#### illini88

##### Member
How do you calculate this. My initial gravity reading was 1.045. Bottling today and will be taking a reading.

Thanks.

#### tnlandsailor

##### Well-Known Member
I pulled this off of another board. This equation agrees with the calculator in Promash (or at least close enough).

Alcohol by Weight(abw) = (OG-FG) * 105

Alcohol by Volume(abv) = abw * 1.25

So for your beer, take 1.045 and subtract your gravity reading, multiply by 105 and then multiply the entire result by 1.25 to get %ABV (most everyone means %ABV when they talk about % alcohol.

Prosit!

#### Sasquatch

##### Well-Known Member
Holy cow I just read em off the chart on the hydrometer and subtract the difference!

#### andre the giant

##### Well-Known Member
Someone here or elsewhere mentioned this site a while back.

http://www.mrgoodbeer.com/carb-cal.shtml

You just type in the OG, FG and punch "calculate" and you get calories, carbs, ABV, ABW. Its a nice quick way to find out how much weight you'll be putting on, and how drunk you'll get doing it.

#### Rhoobarb

##### Well-Known Member
The formula I have used is to calculate ABV is one I got in a Coopers ale kit a long time ago. I know it by heart:

OG - FG -/- 7.46 +.2. You drop the decimals. Eg: 1045-1012 = 33 -/- 7.46 = 4.42 +.2 = 4.62% ABV