Cookie, the panel itself is about 20"x20". In order to calculate the total panels needed correctly, I would need to know the height as well. But making an educated guess of the ceiling height of 9 feet, you would need about 6 boxes to cover the whole wall. The panel is very easy to install as we have adhesive on the back of the panel, you just need to peel off the protective cover and stick them to the wall. And yes, you can cut the panel easily with heavy duty scissor. hope this helps.