Baking Pan Conversion

Am going to bake an apple cake. The recipe is for a 9X13 pan. Do I need to make any adjustments if I split it into two 9" pans?

Hmm, I don’t think so. Oftentimes, I halve a recipe that calls for that size pan into an 8" or 9" square baking dish. So I think you should be OK. If anything, maybe check around for cooking times for a smaller recipe in a 9" pan or keep it simple and maybe check 5 minutes sooner than the baking time for the original recipe. I’m thinking of even a Duncan Hines box mix, it would provide different baking times for 2 smaller round cakes vs. 1 9 x 13". Happy baking!

ETA: Just for example, here’s an apple cake in a 9" pan you might use as a comparison for ingredients and baking times. Hope it helps.

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Thank you! I know I’ve done this before with this recipe, but couldn’t recall if I had to tweak anything other than the baking time. I’ll post the recipe later (it’s a good one!).

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Cool, look forward to checking it out! :slight_smile:

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That depends on the depth of the 9" pans. Volume of 9x1.5 pan is 6 cups, volume of 9x2 pan is 8 cups whereas volume of 9x13 pan is 14 cups. If the batter depth is changed the cooking time will need to change; a deeper batter will require longer time a slightly lower temperature, a shallower batter will require shorter time and slightly higher temperature.

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Oh, excellent points! I’ll measure the depth. Thank you, Ferny!

uhmmmm, you’re making a recipe that is going to end up with a fixed amount of volume.

the alternative is to just keep making more stuff until the pan is full? unlikely approach…

so you have the same number of cups / cubic inches / etc but using the two pans that volume will spread out over more area and the resulting cake will be thinner.
9x13 = 117 sq inches; 9x9=81 sq inches, times 2 pans = 162 sq inches

thinner will bake quicker than thicker.


Thank you all for the guidance. Cakes baked well in the 9" pans - were done at 47 minutes (in a 9X13 it was supposed to take an hour). Tasted marvelous. Will post the recipe separately and add photos when I get them off my phone.

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your math is mixed-up here. 2 pans don’t make more surface area. each pan is its own thing. a smaller pan has lesser volume so will cook more quickly. as evidenced by the op’s result.

I’m terribly sorry - but my math and the concept is precisely correct.

not sure what part of 162 square inches is not equal to 117 square inches is unclear, but they are not the same. two pans filled to the same depth as a single pan will cook (almost) identically - but that is not the situation in this case.

the volume produced by a recipe will be thinner when spread out over more square inches - whether that is one bigger pan or 25 smaller pans - and will cook/bake quicker - as you quoted me.

due to edge effects, the more pans, the more lineal inches of sides and the more even faster the fixed volume of a recipe will bake.

The unknown variable here is the volume of the original cake, hence the volume of the replacement pans make a difference. The 9x13 pan has a fixed volume that is larger than the sum of the volume of two 9x1.5 pans, and smaller than the sum of the volume of two 9x2 pans. Since the unknown is the volume of the cake, it is unknown how deep it will end up being once split between two pans. If it approaches the volume of the 9x13 pan, it will exceed the capacity of the two 9x1.5 pans, but will be smaller than the capacity of the other pans. The depth of the batter is what matters in baking.

the volume of the pans proper - presuming they are high enough to contain the batter - is irrelevant.

the baker is NOT making more and more and more batter to fill either the 9x13 or the two 9x9 pans to the brim.

when you pour X cubic inches into a pan of 117 square inches it will fill the pan to a depth = X divided by 117

if you pour the same volume of X cubic inches to one pan or five pans - equally - that in total are 162 square inches, the depth in each pan will be X divided by 162.

now, if X is the same number, is
X divided by 117
deeper or less deep than
X divided by 162

you are correct the volume of the batter is unknown. but the depth when equally split between the two 9x9 pans is not unknown.

it is (117/162=) 72.2% of the depth in the 9x13 pan.

You don’t know the volume of X cubic inches! Let’s assume 14 cups of batter and split it between two pans, It won’t all fit in two 9x1.5 inch pans. It will all fit into two 9x2 pans, but if using 9x1.5 pans the depth will by necessity be shallower in the 9x1.5 pan because you cannot fill cake pans to the top, space must be left for the cake to rise. So the 9x1.5 pan must receive less batter than the 9x2 pan, which can accommodate the entire 14 cups of batter with room for rise. As a consequence the 14 cup cake baked in the 9x1.5 pans will have to be shallower than the cake baked in the 9x2 pans. There will be excess batter that cannot fit in two 9x1.5 pans, but no no excess batter if 9x2 pans used. It is simple math, but you cannot ignore the variable of the volume of cake batter. If the cake batter is 10 cups, then you are correct, both pans will have batter the same depth. But if you assume the baker is making a recipe for a 9x13 pan with no tweaks, it is a fact that the 9x13 pan has a greater capacity than the sum of two 9x1.5 pans, then you must recognize the possibility that the resulting volume will be more than can be accommodated in smaller pans. A pan with more depth will accept more batter resulting in a cake of greater depth requiring longer cooking time and a slightly lower temperature than a shallower pan and a cake of shallower depth. The half-inch difference in pan height makes a difference…

why are you assuming that a 9" pan would be less full, i.e. thinner batter, than a 9x13?

i guess we agree that 2 pans cook more quickly than one bigger one but you seem to be getting there in a very convoluted way.

sorry folks. the point that is being missed is:

the OP makes a recipe.
that recipe make a given volume.
that given volume of batter does not change whether is is poured into one 9x13 pan or two 9x9 pans.

“why are you assuming that a 9” pan would be less full, i.e. thinner batter, than a 9x13?"
I’m not; he assumption is, per the OP, two 9x9 pans.

the OP clearly states the recipe calls for a 9x13 pan, and the OP wants to use two 9x9 pans, and it worked. the assumption that the volume of batter such that half the batter will not fit in a 9x9x1.5, and the remaining (more than half) will fit into a 9x9x2 pan, thus making the baking time shorter / long / different is completely outside the discussion. if the point is to make assumptions to prove some theory, then I’m going to bake the cake in my Tardis, because it is bigger on the inside than the outside and all these issues go away.

the question is not about the volume of the pan(s) - the length, width, depth of any or all of the pans does not change the volume of batter created by the recipe.

the definition of volume is area times thickness: V = A x D
I don’t know how the new math works, but in the old math if the volume of batter stays the same and it is spread out over a bigger area, the thickness must decrease.

  • and two 9x9 pans have an area of 162 sq inches vs one 9x13 pan with 117 sq inches.

The volume of the batter stays the same; when it is poured into two smaller pans, the sum of the volume of batter in pan1 and the batter volume in pan2, does not necessarily equal the original volume; there may be unused batter, depending on the pan size chosen. We don’t know how much batter the OP’s recipe produced nor how thick the cake batter was when poured into the 9x13 pan.

But we do know the volume of that pan and the volume of two alternative sized round pans. The total capacity of the pans must be taken into account, not merely surface inches, since the original volume may be greater than the combined volume of two smaller pans. The variable is what is the volume of the original recipe. It is the unknown variable. It is not possible to split 14 cups of batter into two 6 cup pans. You cannot put 7 cups of batter into one 6 cup pan. There is excess batter that cannot be used because it doesn’t fit.


I’m outta here.

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