Special circumstances (cathedral ceilings, stairways, etc.) will need a professional estimate. Exact estimates can be obtained by contacting us, or if a professional will be doing the installation, they will provide this service. Estimation Example 20' + 20' + 15' + 15' = 70' room circumference 70' x 8' ceiling height = 560 sq. feet 560 / 25 = 22.4 single rolls 24 single rolls is how much to order including 5% waste Estimation Method The first step is an accurate measurement of the walls that are to be covered. Use a yardstick or steel tape measure. Measure in feet rounding up to the next half or whole foot. Above is a diagram showing a generic room to illustrate how this estimation takes place. First, add together the length of every wall that will be covered then, multiply this number by your ceiling height.