Use this calculator to determine your wallpaper needs. Details

Enter measurements Room perimeter: ft. Wall height: ft. Single doors: 20 sq. ft. Double doors: 40 sq. ft. Small windows: 10 sq. ft. Large windows: 25 sq. ft. Other areas: sq. ft. Roll size: sq. ft. per roll Your results Rolls needed: Allow 5% more material for waste.

To estimate the amount of standard American wallpaper you'll need, first add up the lengths of all walls to get the distance around the room and enter this figure as the perimeter of the room. Round off to the nearest foot. Next, enter the number of single doors (about 20 square feet), the number of double doors (about 40 square feet), small windows (10 square feet) and large windows (25 square feet). Also enter the square footage of any other openings or areas not to be wallpapered -- such as a fireplace.

Next enter the size of the roll of the paper you're using in square feet, and click on "calculate." The calculator will tell you how many rolls of that size are needed. A standard American roll of wallpaper gives you about 35 square feet, but waste and pattern matching usually takes this down to about 27 usable square feet per roll.

Two wallpapering tips:

• Always buy paper that carries the same lot, run or batch number. And buy more of it than you need. In addition to a pattern number, wallpaper usually is labeled with the lot, batch or run number, which indicates all the colors in that batch will be consistent. The same color in a different run or lot may be noticeably different. Buy more than you need so you'll have matching colors if you need to repaper or make repairs in the future.
• Some waste is created when the paper must be dropped down to match the pattern on the panel just installed. To minimize this problem use two rolls at a time and alternate.