The One Evil Pilsner recipe uses (2) 1.21 lb cans of extract (2.42 lbs total) and 'claims' to yield a brew with about 4.6% Alcohol by Volume (this assumes the correct amount of water is used... Generally though, it has been my experience that you may under achieve that value... Or even overshoot it if you use too little water).
With extract brews, one can usually expect about 75% attenuation so its real common for a beer that starts out with an OG (Original Gravity) of say, 1.040 to attenuate to about 1.010 (Final Gravity) and yield about a 4% beer.
So, here's how this works...
Just read the original specific gravity of your beers just before you pitch the yeast and record it...
(Note: If your hydrometer has an ABV scale and or Brix scale, don't use those scales for beer... They generally are for winemakers... Stick to the specific gravity scale!)
Then, take a reading after about 16-17 days... The take a third two days later...
(Can your beer be done attenuating before this? Yes! But if you figure a total fermentation time of 21 days instead of 7-14 days, your beer will be better because the yeast will have had time to clean up after themselves and reduce compounds that can produce off flavors. If your OG is significantly higher as in stronger beers, you might even ferment for up to 30 days or so)
Once the readings are the same two readings in a row, your beer is ready and you can consider the reading to be your FG (Final Gravity). This means that the yeast have eaten all they can and you are ready to bottle.
To determine the overall ABV of your beer, you can use an online tool.
My favorite is our own Screwy Brewer's website:
http://www.thescrewybrewer.com
Just click on Brewing Tools and Formulas to get to Screwy Calc!
Punch in your OG, FG and temps and hit calculate. Voila!
