This is very easy to do with a kitchen scale. First, figure out how much cake batter or frosting you need by going to this calculator. It takes the shape (square or rectangular or cupcake pan) and dimensions into account. Next, compare it to this recipe's ingredient list which makes 6 cups of batter. For example, if you found out you need 8 cups of batter—multiply each quantity by 1.3 (8 / 6). Or if you only need 4 cups, multiply by 0.67