How to determine ABV?

[birdley123]

I know Ive read this somewhere, and for the life of me I cant figure it out.
Just finished my third batch. How do i calculate the ABV of my beer?

Thx,

 

[user 108580]

Did you take gravity readings? I use OG (original gravity) minus FG (final gravity) divided by 7.5 so:

OG: 1.055
FG: 1.010

(55-10) / 7.5 = 6% ABV

 

[TwinsBrewers81]

Take a gravity reading using a hydrometer before pitching your yeast but after cooling wort to your desired yeast pitching temperature. Let fermentation happen, use your hydrometer to take another reading after fermenation is complete (same gravity reading 3 or mor days apart). Use one of the many calculators out there like this one http://www.brewersfriend.com/abv-calculator/

Or better yet watch this...

 

[dmashl]

OG -FG X 131.25=ABV

Ex. 1.051-1.012 X 131.25 = 5.11%

 

[DocScott]

(OG - FG)*131 = abv. Quick, easy, and pretty darn accurate!