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A useful tip for scaling recipes
http://cookaholics.org/viewtopic.php?f=12&t=3011		 Page 1 of 5
Author:  BeckyH [ Wed Mar 06, 2013 3:33 pm ]
Post subject:  A useful tip for scaling recipes
Say you want to scale a recipe to make a larger batch. I find recipes for 9x13" pans, but want to bake 18x24" trays. So:
I multiply 9x13 and get 117.
I do the same for 18x24 and get 432.
Then I divide. The scaling factor, as I call it, is 3.7.
I multiply each ingredient by 3.7 to get the amount I need.
You can build a chart of scaling factors for the sizes you use the most.
Author:  auntcy1 [ Wed Mar 06, 2013 5:29 pm ]
Post subject:  Re: A useful tip for scaling recipes
Excellent! Thanks Becky!
Author:  Cubangirl [ Thu Mar 07, 2013 4:08 am ]
Post subject:  Re: A useful tip for scaling recipes
That is pretty useful Becky. I assume it would work down as well e.g. 9" X 13" to a 7" X 10" would give you a 0.598 multiplier.

Would it work for round pans? If so what would you multiply. I get the math, just not sure what number I'd use to start.

I always had to start with volume before I got LC that did the scaling for me. If total volume was 6 cups. and the original had 1 cup milk then I'd do 1 is to 6 as X is to 9=1.5. It is nice not have to know the volume.
Author:  jeanf [ Thu Mar 07, 2013 7:06 am ]
Post subject:  Re: A useful tip for scaling recipes
My math teacher is laughing somewhere right now, thinking "Told you this would come in handy"
Author:  JesBelle [ Thu Mar 07, 2013 8:09 am ]
Post subject:  Re: A useful tip for scaling recipes
Awesome! Now, how do you do round pans? I'd like to make a small pi.


(I slay me.)
Author:  Amy [ Thu Mar 07, 2013 8:16 am ]
Post subject:  Re: A useful tip for scaling recipes
Well, pi day is coming up...

You slay me too.

Amy
Author:  Paul Kierstead [ Thu Mar 07, 2013 10:01 am ]
Post subject:  Re: A useful tip for scaling recipes
The calculation is based on area (and assumes you are making the recipe to the same depth regardless). The area of a round pan (say... a pie pan) is pi * r^2 or pi * r * r. Now normally pans are given in diameter, so more usefully it is pi * d * d /4. We can use 3.14 for pi, and dividing by 4, we get 0.785, so our final calculation is 0.785 * d * d. So, for a 9" round pan, your number would be:

0.785 * 9 * 9

or 63.585

This is Becky's scaling factor. So, if you recipe was designed for 9x13 (117 scaling factor), and you want to make a 9" round pan instead, use 63.585/117 or 0.54 scaling. So basically you would use half the ingredients.

If that is way too long to read, then here is the short version:

The scaling factor for round pans is 0.785 * d * d where d is the pan diameter.
Author:  Cubangirl [ Thu Mar 07, 2013 10:04 am ]
Post subject:  Re: A useful tip for scaling recipes
I was a math major, so I love this stuff, and should have been able to figure it out, but it has been a while since I used my brain that way. I was trying to a void having to the diameter bit. I also caught that pans had to be the same height. Thanks Paul.
Author:  Da Bull Man [ Thu Mar 07, 2013 10:36 am ]
Post subject:  Re: A useful tip for scaling recipes
Sooo...who is going to put together the generic Excel spreadsheet?
Author:  Amy [ Thu Mar 07, 2013 10:38 am ]
Post subject:  Re: A useful tip for scaling recipes
I vote for Jim.
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