Wallpaper Calculator

Enter your room dimensions, number of openings, and wallpaper roll specifications to calculate exactly how many rolls you need. Includes automatic waste adjustment for pattern repeats.

Estimate only — not professional advice. Always verify results independently before purchasing materials or beginning work. Terms of Use

What is Wallpaper?

A wallpaper calculator determines the number of rolls needed to cover the walls of a room, accounting for doors, windows, and the waste inherent in pattern matching. Accurate estimation prevents the costly mistake of running short mid-project (dye lots vary between production runs, making exact color matching impossible with a later purchase) or over-buying expensive designer wallpaper. The calculation starts with the gross wall area: room perimeter multiplied by wall height. Standard doors are estimated at 21 square feet each (3 ft x 7 ft) and standard windows at 15 square feet each (3 ft x 5 ft). These openings are subtracted to produce the net wall area that actually needs covering. Wallpaper is sold in single rolls and double rolls. A standard American single roll is 20.5 inches wide by 16.5 feet long (about 28 square feet of gross area, or roughly 24 usable square feet after trimming). A double roll is 20.5 inches by 33 feet (about 56 square feet gross, or roughly 48 usable square feet). European rolls are typically 21 inches wide by 33 feet. The calculator defaults to a 21-inch by 33-foot double roll, which is the most common retail format. Always check your specific product dimensions, as widths range from 18 to 36 inches and lengths vary by manufacturer. The calculator reports Usable Roll Coverage, not gross roll area. Even with plain (non-patterned) wallpaper, you lose paper to trimming at the ceiling line and baseboard, the unusable offcut at the end of each strip, and edge alignment. This calculator applies a 15 percent derate to the gross roll area, so a 21-inch by 33-foot double roll with a gross area of 57.75 square feet provides about 49 usable square feet. Rolls needed are computed against this usable figure, which prevents the common error of under-ordering when a calculator divides net wall area by gross roll area. Pattern repeat is the distance between identical points in the wallpaper design. A 12-inch repeat means the pattern repeats every 12 inches vertically. When hanging patterned wallpaper, each strip must be aligned to the adjacent strip, which creates waste at the top and bottom of each cut. The industry standard waste allowance for patterned wallpaper is 15% above what a plain wallpaper would require. Papers with no pattern (solid colors, textures, random designs) have zero waste from matching. Professional wallpaper hangers typically recommend adding one extra roll beyond the calculated amount as insurance against cutting errors, damaged sections, and future repairs. Leftover wallpaper from the same dye lot is invaluable for patching damage years later. This calculator provides the mathematically correct number — consider adding one roll for safety. The quality of the substrate matters as much as the quantity of paper. Walls should be smooth, primed with wallpaper primer (not paint primer), and free of texture. Textured walls dramatically increase waste because the paper does not adhere smoothly and may require stripping and skim-coating before installation.

How to Calculate

1. Measure the total perimeter of the room in feet (sum of all wall lengths)
2. Measure the wall height from floor to ceiling in feet
3. Count the number of standard doors and windows in the room
4. Check your wallpaper specifications for roll width (inches) and roll length (feet)
5. If the wallpaper has a pattern, enter the pattern repeat distance in inches (found on the label)
6. The calculator shows gross area, net area after openings, and rolls needed

Formula

Gross Wall Area = Room Perimeter (ft) x Wall Height (ft) Door Area = Number of Doors x 21 sq ft (standard 3 ft x 7 ft door) Window Area = Number of Windows x 15 sq ft (standard 3 ft x 5 ft window) Net Wall Area = Gross Wall Area - Door Area - Window Area Gross Roll Area = Roll Width (in) / 12 x Roll Length (ft) Usable Roll Coverage = Gross Roll Area x 0.85 Rolls (plain) = Net Wall Area / Usable Roll Coverage Rolls (patterned) = Rolls (plain) x 1.15 The 0.85 multiplier derates the gross roll area by 15% to account for trimming at the ceiling and baseboard, end-of-strip offcuts, and edge alignment — even plain wallpaper cannot use the full printed area. Rolls needed are always computed against this usable coverage. The separate 1.15 multiplier adds an additional 15% waste when a pattern repeat is specified (industry standard for pattern matching waste). If pattern repeat is 0, no pattern-matching waste is added (but the usable-coverage derate still applies).

Example Calculation

A room with 56 ft perimeter, 8 ft ceilings, 2 doors, 3 windows, using 21-inch by 33-foot double rolls with no pattern repeat: Gross Wall Area = 56 x 8 = 448 sq ft Door Area = 2 x 21 = 42 sq ft Window Area = 3 x 15 = 45 sq ft Net Wall Area = 448 - 42 - 45 = 361 sq ft Gross Roll Area = (21 / 12) x 33 = 1.75 x 33 = 57.75 sq ft Usable Roll Coverage = 57.75 x 0.85 = 49.09 sq ft Rolls = ceil(361 / 49.09) = ceil(7.35) = 8 rolls

Frequently Asked Questions