How do you calculate the hardcover size?

Is the hardcover trim size a certain amount larger than the page size?

The interior page size/book block size is the trim size, then we produce a 1/8" overhang for the boards on all sides. 

For example, a book with a 7" x 8-3/4" trim size would result in a board height of 9". For the board width you need to subtract the hinge of .56"  from 7.25" and it will result in 6.69". Our templates will display those dimensions (ask your CSR for a template). For larger trim sizes the hinge width will slightly change.