how do i effectively multiply a recipe from filling a 8x8 sheet to a Full sheet pan:  26 x  18 x  1 and a Three Quarters sheet pan, which is 21 x  15   x1?

Thank you, so so so much!


(its for a nanaimo bar, if anyone was curious)

well this is a little of a pain in the butt, what i have done in the past is mix up one batch of the batter and then measure how many cups it is, then i count how many cups of water it takes to fill the pan up. then i know how many times i need to multiply the recipe

There's a far easier way: math! If the recipe you have fills an 8x8 square, then that's 64 square inches. If the pan you need to fill is 26x18, then you need 468 square inches. 468 divided by 64 is 7.3. You need to multiply your recipe by 7.3 (or you can round up to where the numbers make a bit more sense and you aren't using .35 eggs or something)

Yes, my math was assuming that the depth of her final recipe would be the same (since she said she was baking a bar and didn't give other depth info). YES if you are changing depth as well, you will need to add that to the math.

To expand:
The 8x8 pan (surface area) is 64 SQUARE inches. At a 2" depth, it's 128 CUBIC inches (8x8x2).

The 18x26 pan at 2" deep is 936 CUBIC inches and 936/128 is still 7.31. It's important to keep apples to apples.

And in addition to all of the above, one of the most important things I have ever done, is write down exactly how many pans (square, round) each recipe fills. Not how many cups, not how many square inches, but true life pans. I have no less than 20 different entries on each page of my recipes that tells me something like this:

2 times the recipe makes 2-8" rounds, 2-10" rounds, and 1-4" round
or
2 times the recipe makes 1-12" round, 2-5" rounds, and 2-7" rounds, and 2-4" rounds.

I can glance at every one of those scenarios when I get ready to bake, and figure out about how much I need to bake for each order. If I come up with a new set of "how much this recipe made", I'll record that as well.

Hope that made sense.

Or you could just pour water (a cup at a time) into the 8 X 8 so you know exactly how many cups you use, then do the same with the 26 X 18 to see how many it will take and do the math.

King Arthur Flour has a page that explains how to multiply/divide recipes. I would figure out the number of square inches of batter/dough you need for the 8x8 and divide that into the square inches for the other two sizes. This will give you approximately the number of original recipes you'll need. Then use the calculations from this page to determine ingredient measurements:
http://www.kingarthurflour.com/professional/bakers-percentage.html

HTH.

You all lost me on post 3. I have nothing to add, just that my eyes are crossed now, thanks

And they say "baking a little cake" doesn't take any smarts!

I use The Cake Bible's charts. She has a section for professionals and passionate amateurs that breaks down how to scale a recipe for every size pan from 6 inches up to 18 inches and sheet pans. It is for round pans, but I find that for square pans I use the next size up. ie, if you need an 8in square, use the 9inch round recipe.

Well, StormyHaze - did we actually help or just confuse the crap out of you?! lol

I do the math too, depth and surface area, but rather than split eggs, I use the closest whole or half recipe. But I use these extras to make cupcakes for samples. The extra batter is my way to sample with no extra work.

On round recipes, you have to use pi r squared.

If you want to know an answer without doing the math, I always answer those posts, as do others. You can always just post the two pan sizes and we will do the math for you.