Thank you Fred,
That was what my idea was to do is buy a couple of packages of the curves to make sure about the room. The layout I found online has all the sizes marked in what I need.
Thanks again for your input!

If I had 30" wide to fit the 12.50 radius, will I still be able to use the 11.25 radius for the inner loop?

I am planning on building an N scale layout. I am limited on space. My platform will be 26" to 28" wide and 7 1/2 feet long. To be able to operate two ovals will I be able to use 12.5 radius on the outer route and run longer train and the 11.25 on the inner and run shorter train? I found a layout on line. The inner line will have a switching yard. Switches will also be installed so trains can switch from outer loop to inner loop.