How much would 20 percent of salt be in a gallon of water be?

To find 20 percent of a gallon of water, first note that a gallon is equivalent to 128 fluid ounces. Twenty percent of 128 ounces is 25.6 ounces. Therefore, if you were to make a 20 percent salt solution in a gallon of water, you would need to add 25.6 ounces of salt.