Confectioners’ sugar is the American name for icing sugar: white sugar ground to a fine powder, often with a small amount of anti-caking starch. Its powder fineness dissolves instantly, making it ideal for icings, frostings, dusting desserts, and sweetening whipped cream, where granulated sugar would stay gritty. It is the basis of royal icing and buttercream, giving smooth, professional finishes. Because the particles are so fine, it must be sifted before use to remove lumps. Like all sugars it is pure sucrose with the same calories, differing only in crystal size and convenience.