An Alternative Method
Another method much favoured by some paper-hangers is as follows. The height of the walls to be covered is measured and, if it is not more than 7f feet, it is safe to assume that each piece will cut four full lengths. If the height is more than 8 feet and not more than 10 feet, the rolls will each provide three full lengths.
Remembering that the lengths are all 21 inches wide, it is easy to calculate how many full lengths will be required. The total number of full lengths required is then divided by three or four as the case may be, and the resulting figure is the number of pieces required.
For the purposes of this kind of calculation, all sho# lengths required for over doors and above and below windows are ignored, as there will be some surplus from each piece that will suffice to cover these, but it is advisable to count those over the mantelpiece as full lengths.