I have used SCARM to design all my layouts. The free version permits a layout with up to 100 pieces of track. This tutorial shows how to use the free version to create an interesting layout and generate a parts
Giant v11 & v16 Kato N Scale Layout
This is my first layout in the new room that comes close to using all the available space. If I moved some furniture, I could add another five feet to the layout, but I have plenty of space without doing