Baking a cake in a larger/smaller pan

Question

Is there a guide or rule of thumb about scaling a cake. If the recipe calls for an 8-inch square pan and I use a 10-inch square pan, how will it behave in the oven? I expect the baking time will be longer but should I change the temperature for more even baking?

Note: I already realize that a 10-inch pan will requires roughly 1.5 times the batter than is called for for a recipe designed for an 8-inch pan. for square pans: (10 * 10) / (8 * 8) = 100 / 64 ~ 3/2 for round pans: (pi * 5 * 5) / (pi * 4 * 4) = 25/16 ~ 3/2.

Answer 1

Within reasonable limits, baking time is proportional to the thickness of the cake.

If you scale your recipe proportionately to the change in surface area from the standard pan to the one you are going to use, the baking time will be approximately the same. You can continue to use the base time as a guideline, but as always in successful cooking and baking, you will want to test when the layer is done with an appropriate method, such as the toothpick test.

On the other hand, thinner layers require less time, and counter-intuitively, higher temperatures; thicker layers more time and lower temperatures. You should not see this requirement if you are scaling based on pan surface.

When you begin to make very large layers, as for a wedding cake, changes to leavening will also be required.

Answer 2

Here's a little table of cake pan sizes in inches and square inches:

Cake pan sizes, with square and circular areas  

inches  square  circular
5       25      19.6
6       36      28.2
7       49      38.4
8       64      50.2
9       81      63.6
10      100     78.5
11      121     95.0
12      144     113.0
13      169     132.7

Columns:

1. inches is the length of a side of a square, or the diameter of a circle.
2. square is the area (in square inches) of a square with inches sides.
3. circular is the area (in square inches) of a circle with a diameter of inches.

Example: If a recipe called for for a 9" circular pan, (63.6 sq. inches), and the only pan that was available was an 8" square pan, (64 sq. inches), that'd be a close match.

Generally substituting an n" square for an n+1" circle, for area gives a +/-10% margin of error.

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Perimeters are less interesting for cake, but might be of interest with pizza crust.

Equivalent diameter circles always have 21% less perimeter than squares.

Not so for an n" square and and n+1" circle, where the perimeter percent difference increases with size. For example an 8" square pan has a 32" perimeter, a 9" circle has a 28" perimeter, a 12% difference; but the perimeter of a 9" square is 13% larger than that of a 10" circle. This perimeter percent increase gradually slows down and levels off at 21% at and above 83".