This program will calculate the amount of drywall needed to drywall an area or a room assuming there is no waste. For ceiling height, measure from floor to ceiling. If you are NOT drywalling the ceiling you may omit entering the ceiling height. For example, a room 10 x 15 feet with a ceiling hight of 8 feet would require 17.1875 sheets or 550 square feet.

Consider adding a 10 percent waste factor to your final calculation.
For highly complex installations allow 20%.