The answer to how many square feet in a roofing square is simple: one roofing square equals 100 square feet of roof surface. That sounds straightforward, but getting from your home's dimensions to the correct number of roofing squares takes more than dividing the floor area by 100. Roof pitch, overhangs, dormers, valleys, and separate roof planes can all change the actual area that needs roofing material. Understanding the measurement helps you make sense of roofing estimates