Here are a few simple formula to help you determine the amount of alcohol in your brew.
Percentage of Alcohol by Volume = (Original Gravity - Final Gravity) / 0.75
For example our readings on a :
Original Gravity or OG = 1.048
Final Gravity or FG = 1.007
The equation would look like this:
0.0546 = (1.048 OG – 1.007 FG) / .075
In this example your beer would be about 5.4% alcohol.