Hello, I am new to the site and still a novice baker. Can anyone tell me how to convert ingredient measurments from a 9” pie to a 9.5 in. pie? Is there an easy, go-to formula?  My jr. high school math skills tell me that 9 in. is about 94.7 % of 9.5 in., so is it simple enough just to convert all the ingredients with that number?

Assuming that the depth of the plates is about the same, you can just work with circle areas ( the old “pi r2”).

For the 9 inch pie, just multiply everything by 1.114 to get the amount for the 9.5 inch pie.

Math:

9 inch = 4.5 x 4.5 x 3.14 = 63.585
9.5 inch = 4.75 x 4.75 x 3.14 = 70.846

63.585(X) = 70.846
X= 1.114

Ya know, I thought baking would just be fun and therapeutic . . . now you have to go and inject math into the darn process. Just kidding, even math challenged as I am, I think I can handle the “pi” and the “pie”. Thanks for your help . . . see you in the kitchen!

For those of us who would prefer to be baking rather than delving into mathematical pies - there is a quick on line calculator:

http://math.about.com/library/blcirclecalculator.htm

Hey Paul, isn’t that along the line that we discussed yesterday?

Bakemeadowlane - I do the same as Matthew, except that I leave out the PI as it’s the same above and below the line. So to convert, I quickly do the following:
<baking form diameter> x <baking form diameter> / <recipe diameter> / <recipe diameter>  I then save that number and multiply all the ingredients with it. I made a 4 layer wedding cake using this math and it came out as expected…. (Trrrrrust me, I’m an engineer!!!!)

If you want to split hairs: For a pie you need to fudge the multiplication factor for the dough a little, as you’ll need about half the dough for the wall (correct me if I’m wrong guys….). So if your baking form is larger than what the recipe calls for I’d go a bit lower on the number, and if you’re using a smaller form go a little higher, i.e. if you’re using 6” instead of 9” my formula would give you 0.444, where I’d probably up the dough to 0.5 or 0.55 to be on the safe side. I wouldn’t worry too much about the 9.5” pan, I’d just use 1.1 time the ingredients.

Btw, Google has a handy calculator built in, just enter 6*6/9/9 in the search line and it spits out the result.

Clever tip about leaving out pi—I never thought of that!

Oh, and I also use the diameter rather than the radius. Of course that won’t work if you’re comparing a round form with a square form, in which case you’ll have to go with the full enchilada - eh, formula for the area of the circle.

Hi Silke it was Bakemeadeowlane’s post but I thought I would chip in.

I was studying Pi last night (midnight) - last did these calcs more than 40 years ago. Maths, Geom, and Trig were not my strong points then and they aren’t now!

So we are humbly MOST grateful for your kind assistance and clear explanation.  As Matthew says leaving out Pi is a very neat trick!

Thank heavens were not dealing with pyramids and cylinders. Oh wait the dreaded tube cake/bundt lies ahead!

I do feel with your help the administrators of this site should compile a sticky on this topic. It seems to come up continually.

Thanks Paul - that’s the advantage of having an engineer on the forum

Tube and bundt are easy, they are usually rated by cups, both when you buy them and when you look at the recipes. This is very easy to convert, the multiplier is simply <cup measurement of your form> / <cup measurement in recipe>. The cooking time will have to be adjusted, though, but in the RHC there are usually additional pointers on when the cake is done, by color or if it pulls away from the side of the form.

Would you believe it that our tube and bundt pans here are only sold by the diameter - no cup measurement. I think anyone who bakes outside of the US deserves a medal. This feels like an unending obstacle course!

Maybe I will buy some, take them home, fill with water to cup measure, dry and return the unsuitable ones to the shop. The best selection of pans is on line which makes returns impossible here.

Yikes pass the double scotch!

Silke thanks again for your help.

They are sold in CUP sizes in the States because that’s how they measure.  Nowhere else in the world, as far as I know, measures like this, we use scales!

Oh! I see Jeannette makes sense for the US. Maybe Rose will start a baking revolution.

I’m with you Jeanette. I was utterly confused when I moved here why you would measure out 1/2 CUP OF BUTTER? What a strange concept. Eventually I looked on the packages and the tablespoons are marked on it, which makes it easier but still not very logical. While I still stay away from baking recipes with cups I have to say that it makes sense when it comes to Bundt and tube pans, a volume measurement (cups or liters or ccm or whatever) is better than a diameter…

But then it was you guys who started the whole English measurement system, right?