HELP!!! PRINCESS CASTLE CAKE

Well, have you seen a picture that resemble the look you want? Because the proportions of the cake design will come into play along with the serving sizes. Personally I would think that to get a square cake with a round cake on top to achieve the castle look, you are going to end up with a lot of extra cake. Often people use a dummy cake as part of the effect to get the height.
But most importantly since there are so many styles of castle cakes out there, I think you need to first show us what style you are going for before we can help you with cake pan sizes.
Hugs Squirrelly

If you have a look in my photos there is a princess castle cake...it is a 4 tier stacked cake..and each layer is duble stacked.....

I made it in two days...and is plenty enough for the amount of guests you have......

If you need any info just let me know

Rach

Glad you like the cakes...It isnt too bad too do so if you do decide on it ..just let me know and I will try and help you..

Rach

All you do is ice the cakes ..I use sugarpaste let them dry for 24 hours then stack.....cos the cakes arnt too big I dont even dowel them and they are fine......I used and 8,6,4,2 inch the 2inch was just sugarpaste..All the cakes are double cakes to get the height..so each layer is a lovely thick cake.....

Also I place each cake on a cake card..just a thin board the same size as the cake ie 8,6,4 fill and ice on those then when stacking gives extra support and it also makes it easy to lift off each layer to cut

Well, you will want them fairly high for proportion so perhaps each cake 6 inches high. Or the bottom square, 4 inches or two 2 inch layers and the top 6 inches high. You will have loads and loads of cake, probably way too much, this is why I asked. Sometimes to avoid a lot of cake people use a dummy for one tier.
You need the height to be able to put the details on and also, it will look more in proportion to the turrets.
The cakes Rach1 did are just gorgeous, beautiful!
The main reason for using dowelling with a two layer cake is serving, yes you can get away without them if the cakes are smaller but particularily with buttercream iced cakes, you want to dowel and board so that the top icing of one cake doesn't stick to the bottom of the board of the cake above. For really small cakes that are covered in fondant, this will work sometimes but not when you get into larger ones of more than two tiers because of the weight factor. One quarter inch of fondant does add some support to a cake in that it increases the density factor. Also the density of the cake you are using will come into play. For a two tiered cake you can get away with using straws for support.
If a cake will be transported, you are also wise to use a centre dowel in the middle. Now a lot of two tiered cakes will be no problem but if you have to brake suddenly, the cake can shift off the top against your box and be ruined. Also your cakes must be very level or the one cake can slide off.
Now do you also have an eight inch round? Because if you do, I would turn the pans upside down and see which one looks best. You may find the eight inch round gives you more space around to house your decorations or the nine inch one may be fine. But with the 9 inch you will only have 1 1/2 inches on either side of the 9 inch round so that might be a factor.
Hugs Squirrelly

Good luck.cant wait to see what you make

Your castle cakes are lovely, wonderful!
Hugs Squirrelly

Its great on here.....everyone so friendly..and loads of pics to look at...

The cakes on here are amazing..got soo much to learn..going to be fun

Glad you are enjoying it here, welcome!
Hugs Squirrelly