This may be a silly question, but I've never understood why square cakes are said to have more servings. I use the same quantities of all ingredients for both round and square cakes, and they're both 4" tall. Is it just because square cakes have a larger surface area?

Because of the corners. Think about it - you can put a 10" round pan *inside* a 10" square pan, for example.

It's all about volume. (Fun with math.)

And I always need to use more batter in a square pan to get a proper cake.

Okay, but thinking about it another way. Both pans use the same amount of batter. The round pans cake will bake up slightly taller than the square pan cake. Let me put it another way. The little bit that fills in the corners in a square cake makes the same size round cake taller, but it's still the same amount of batter. The hall can cut slightly slimmer slices of the round cake and slightly wider slices of the square. Volume remains the same but perception of a difference persists in articles published by authors not associated with the wedding industry.

I don't use the same amount if batter in the pans.

I'm with Leah... I do the math.

If both cakes are the same height, area of the square is l x w. Area of the round is pi r(squared).

Example: 10 inch square cake, area 10 x 10 equals 100
10 inch round 5 x 5 times 3.14 equals 78.5

So in this application, the square takes between 20% to 25% more batter for the exact same height cake.

With this info, you can up all ingredients by 25% or just 1.5x and make a few cupcakes.

This method works perfectly when you want to convert any 8" or 9" cake recipe into a larger cake.

No, you never get the same size cake from the same amount of batter on a square and round pan. Not possible.

Rose Levy's Cake Bible suggests increasing the amount of batter for a square pan by 1/3 of that used for a round pan and I have always found this to be true.

Math doesn't lie. the volume of an 8" cake that is 2" tall is 100 cubic inches. the volume of an 8" square that is 2" tall is 128 cubic inches.

Quick visual. Fill both pans with water to the level you would with batter. Pour water into a measuring cup. There will be more water in the cup from the square pans.

Sometimes you have to see it for yourself.

Math people say "pi" and all I can do is ask "Apple or Cherry?" My husband and daughter do the math for me, I stick to cake, but the math comes in handy when you are increasing and decreasing your recipes without waste or baking millions of extra-batter-cupcakes to take up space in the freezer.

Although, my husband has given me some formulas that I use all the time in baking. I don't quite "get" them, but I plug in my numbers and get my answers. And he gets pie and cake.

Win win.

This is mathematics and there is no debate in numbers. A round and a square will not under any circumstances make the same size cake. She can underbake the square and overbake the round, but given all properties are equal, this will not happen.

Assuming we're talking about a "finished" 4-inch cake (which is the whole point of any serving chart), the height of the layers - when baked - is irrelevant. The layers are going to be leveled before being filled/frosted/stacked.

I definately do not agree that same size rounds and sq pans use the same amount of batter.
A 10" round uses one cake mix batter; a 10" sq uses 1&1/2 mixes (OR one batch of my *original* WASC recipe)
As you go to other sizes, one uses an extra 1/2 batch of batter in the sqs than you do in rounds to have a cake bake up perfectly 2" tall

jgifford, that is not what she described and it is not her question. Of course you can cut a cake to match another cake. That has nothing to do with the issue being discussed.

Sorry too, didn't see that. So she is baking her round more than the square.

The Math:
Goal a 10x4 cake.

Volume of:

Round pan, is pi r^2 h
3.14 x (5^2) x 4 = 314 cubic inches

Square Pan l x b x h
10 x 10 x 4 = 400 cubic inches

There is a 21.5% difference in the volumes of the pans.

The visual:

Bake a 10 in square cake. place a 10 inch round pan on it and try to carve out a 10 inch round cake. You'll have to cut out the edges (some servings) to get the 10 inch round. You will note that the mid sections of each side of the square will match up with the 10 in round pan (because the diameter of the 10 inch round (10 inches) is equal to the length of the sides of the 10 inch square.