Powdered sugar and granulated sugar are one and the same except for particle size. Keep in mind when using volumetric portions that they are NOT interchangeable, but from a functionality standpoint, they are the same. Infact, you can make your own powdered sugar in a food processor.
In case you're wondering (inquiring minds want to know) donut sugar, that stuff that looks like powdered sugar on a cake donut is not actually powdered sugar, even though it is called a powdered sugar donut, or coating. Donut sugar is made with powdered dextrose (not as sweet as sucrose) along with added starch and fat. It is designed specifically for use as a coating sugar on donuts and is never used a a substitute for powdered sugar.
Tom Lehmann/The Dough Doctor