Here's the best way to divide up your frosting between layers.
One key to a great layer cake is balancing the amounts of frosting and cake in each bite, but it’s not that easy. We put too little frosting on one layer and too much on another and then don’t have the right amount to evenly cover the exterior. All that’s needed is a little planning. In general, we recommend a total of 5 cups of frosting for three 8- or 9-inch round layers and 4 cups for two layers. Here’s how to divvy it up.
TIP: Spread the frosting between the cake layers to just past the edges of each layer. This will make coating the sides faster and easier.