HAHA yes I'm baking. Want to double a blondie recipe.

Does the mix stay pretty well below the sides of the 9 x 9? If it does I would think you should be ok. You might want to check that the middle is done.

So your 9x9 pan is 2” deep? And the 15x10 is a 1-inch sheet pan or also 2” deep? If the 15x10 has a 2” depth it should work, but it’s less volume than two 9x9x2 pans. The blondie batter will be deeper meaning a little longer baking time. I’m just thinking it could be too much batter if your pan is 15x10x1. However, as murraysmom asked, you’ll have to check how deep the batter looks if your pan is 15x10x1“. Anywho, sorry for all the math!😵‍💫

And it can make more of difference with baking.

Is your pan for sure 9"x9"? Mine are 8x8x2. I would either just make twice or order a second of the same size pan from big A. A lot of things are coming next day, since they built so many new warehouses.

i went under the assumption that the heigjts are the same or close. I’d prbably double the recipe, fill to the normal height, and put any remaining batter into ramekins and make those for me!

The other day I got to thinking about quiche, for a specific pan I want to put it in. Online recipes are all over the map with regards to egg to dairy ratios, and then within the dairy portion what ratio milk to cream, if any. I ended up having a chat with GPT who explained the different outcomes, and when I decided I wanted to go a little richer than she recommended, she said ok but raise your headspace 1/8 of an inch. I understand why but that struck me as kind of funny.

porkchop, can you just give us the depth of your 15x10 pan? There’s likely a reason the recipe calls for a 9x9 pan vs an 8x8.

@foodonastump I agree with the annoying "all over the map" re: quiche. I make tons of crustless quiche, and the mix that I like the best and use most often is

5 large eggs

3/4 cup half&half

2 cups shredded cheese

whatever veggie or protein you want

season as wanted

bake 45-50 mins, at 350.

rest for 10 mins

9x13 or near that. Just may cooking time a few minutes for something slightly larger or smaller since the depth of the recipe will differ. So you would have a same or slightly longer cooking time for the 9x13 and and a slightly shorter cooking time one for the 9x15

I just made a crustless quiche slightly different dimensions. 9" shallow pie plate, opaque (Corelle) so it won't brown on the bottom like it would with clear. A couple of slender scallions and 2/3 of a bunch of red dandelion fronds, chopped, enough to fill and mound up an inch since the fronds are fluffy and will sink. (Any veg you like will work just fill the dish--my fave is broccolini and red dandelion with spring shallot.) Always 1.75 c milk/cream, I used cream gone to mascarpone along with the whey. 6 whole eggs. Seasoning (Ethiopian and salt). I measure the milk in a quart measuring cup, add the eggs and seasoning and use a non-scratch ball whisk to combine and aerate a bit right in the jug, then pour right over the veg. 4 oz. grated cheese on top (smoked jack this time). 325°F for 55-60 min. until tester comes clean.

No need to guess on sizes. Baking pans are compared by volume. Sally, JOB, and other trustworthy blogs have the charts, as do many of the the pan makers. I keep Joy of Baking's chart in with my recipes

https://sallysbakingaddiction.com/cake-pan-sizes/

https://www.joyofbaking.com/PanSizes.html

https://shop.fatdaddios.com/pages/sheet-cake-pans-size-chart?srsltid=AfmBOopyYfiBB1CkbUR4lJEmPaf0GtOxDWxSuS8PV7fmf21kLGD4eTgD

“i went under the assumption that the heigjts are the same or close.”

Same with me then my thought went to the 15x10x1” sheet pans I have. A 15x10x2 pan could work with maybe a little added baking time due to the depth of the batter increasing just a bit. The total volume there is 300 cubic inches while two 9x9x2 pans give a total of 324. Not much difference. Can’t know for sure but, again, there could be a reason porkchop’s recipe calls for a 9x9 pan (vs 8x8) that I'm assuming is 9x9x2.

Regarding using a 9x13 pan, just thinking it might be a little too much batter for that size. However, as food posted, fill the pan to a safe level (about 2/3 full) then put extra in a smaller pan.

I would use water to fill the 9x9 to the depth the recipe should make, then pour double that amount of water into the larger pan and see how it looks. I'd be more worried that it would be a thinner bar than I wanted, but you'd know to check the doneness sooner.

It's 10x15x2.

I measured the inside of the 9 x 9 pan, and the inside measurement is 8 x 8; outside rim to outside it is 9 x 9. So which size is it actually?

Use the inside measurement.

From Joy of Baking:

To determine the pan's dimensions always measure inside edge to inside edge of the pan so that you do not include the thickness of the pan in your measurement.

To measure the depth, place your ruler straight up from the bottom of the pan (do not slant the ruler).

To determine the pan's volume (how much batter it will hold), pour pre-measured water by the cupful until the pan is filled to the brim.

^Yes, the inside measurement, so you must have an 8x8x2. The inside of my 9x9x2 pans is 9x9. That means your 15x10x2 is a bit smaller than needed to double the recipe for a 9x9x2 pan. Should be fine as long as you watch the baking time (a bit more) and the blondies should be a little thicker. Just keep an eye on them toward the end of baking.

Thank you, all -- very helpful.

Let us know how it goes! Obviously batter amounts can differ from one 9x9 pan recipe to another. The volume difference between two 9x9 pans and one 15x10 is 24 cubic inches less for the larger pan. Just be aware of the batter level in your 15x10 pan.👍🏻

Use a 9x13.

A cautious person would just make the blondie recipe two times and bake it two times in the 9x9 pan. Me, I’d pour a double recipe into my bigger pan and hope for the best.

If your pans measure 9”x9” and 10” 15” outside, they are an 8”x8” and a 9”x13”.

Two 8”x8” are the same as one 9”x 13“.

Two 8x8x2 pans total more volume than one 9x13x2. However, it should work out with the adjustment in baking time as long as the batter isn’t excessive since the recipe calls for a 9x9 pan. If doubling the recipe, a 15x10x2 pan would be a closer fit to two 9x9x2 pans. Again, as mentioned, watching the depth of the batter is key.

There is not a 10x 15 pan. That is an incorrect measurement. It is a 9x13,pan.

"There is not a 10x 15 pan."

There isn't?

^Yes, Pyrex and other options. Also, depending on the brand of pan, the interior should be 15x10, or close…maybe 14.75” x 9.75”. A 10x15x2 pan isn’t exactly standard, but they do exist and are not the same as a 9x13.

ETA - Just thinking…I’ve occasionally halved my lemon bar recipe that calls for a 9x13 pan. I use an 8x8 pan but increase the ingredients by 1/8. You wouldn’t have to as long as you know the baking time would be less since an 8x8 pan is larger than needed for half the recipe.