As of September 2014, Mike's Hard Lemonade Co. makes two brands of drinks: those labeled "Harder" are 8 percent alcohol by volume, while those labeled "Hard" are about 5 percent. Alcohol by volume is a standard measure to calculate how much alcohol is in a beverage.
The alcohol in alcoholic drinks is called ethanol. Alcohol by volume is the number of milliliters of pure ethanol present in 100 milliliters of the drink at 20 degrees Celsius. Another measure of alcohol is called "proof." In the United States, that number is alcohol by volume times two. For example, the "Harder" drink would be 16 proof.