"Baking Science:

You're wrong, and I hope you see this post before you make the cake.
1 Cup = 8 Fluid Oz

When it comes to dry ingredients, "ounces" refers to weight. Most people do not have a kitchen scale, which is why it is written in cups. There is no set "X ounces = Y cups," because everything weighs differently. Example, 1 cup of flour yields about 4.5 ounces, where as 1 cup of brown sugar yields about 7.8 ounces, because it is more dense, and 1 cup of confectioners sugar yields about 3.8 ounces.

As you can see, there is quite a difference. If you don't have a kitchen scale, I suggest using the measurements that are listed in the actual recipe. If they were wrong, there wouldn't be an average of 5 stars with over 250 reviews."