This short video will describe how to read a hydrometer and calculate the percent alcohol in your wine or beer. To calculate alcohol, two key measurements must be taken. The Original Specific Gravity (OG), and the Final Gravity (FG). To take these readings, place the hydrometer in a vial of the liquid to be tested and read to the bottom of the meniscus. Correct for temperature if necessary and be sure to strain juice if it contains many solids.
OG is taken before fermentation and FG is taken after fermentation has completed.
The formula for calculating Alcohol content is (OG-FG)*131 = %Alcohol.
Another way to calculate Alcohol content is (OG-FG)/0.0074 = %Alcohol.
You’ll get slightly different readings with both methods but they’ll give you a good ballpark idea of how much alcohol there is in your wine.