How Much Wallpaper Do I Need?

Step 1: measure the wall area

Add the length and width of the room, double it, and multiply by the ceiling height. Sherwin-Williams gives the same method: (length + width) x 2 x ceiling height. Our own arithmetic for a 12 by 15 ft room with 8 ft walls: 27 x 2 = 54, and 54 x 8 = 432 sq ft.

Step 2: subtract doors and windows

Sherwin-Williams says to take off 20 sq ft for each standard size window or door. One installer site, wallpaperinstaller.com, says not to deduct standard doors and windows at all. The two sources disagree, so the calculator lets you choose. Not deducting leaves a little more paper, which is the safer choice if the pattern is expensive to reorder.

Worked example: one door and two windows is 3 x 20 = 60 sq ft, so 432 - 60 = 372 sq ft.

Step 3: use the usable coverage for your pattern repeat

A single roll does not cover its full area, because you lose paper matching the pattern from strip to strip. Sherwin-Williams gives usable coverage per single roll by pattern repeat: 25 sq ft for 0 to 6 inches, 22 sq ft for 7 to 12 inches, 20 sq ft for 13 to 18 inches and 18 sq ft for 19 to 23 inches. Its table stops at 23 inches, so for bigger repeats ask the maker.

Worked example with a 15 inch repeat: 372 / 20 = 18.6, so 19 single rolls.

Step 4: round up to double rolls

Sherwin-Williams notes that wallpaper is priced in single rolls but is only available in double or triple rolls. 19 singles is an odd number, so round up to 20 singles, which is 10 double rolls.

What a roll measures

Sizes are not standardised. A retailer's comparison chart lists US single rolls as 20.5 to 27 inches wide and 13.5 to 16.5 ft long (about 28 to 35 sq ft), and double rolls as 27 to 33 ft long (about 56 to 70 sq ft). The European roll is 20.9 inches (53 cm) by 32.8 ft (10 m), roughly 57 sq ft. Always check the width, length and repeat on the roll you choose.

How many double rolls for common room sizes

Each row uses 8 ft walls, one door and two windows (20 sq ft deducted each), and the Sherwin-Williams usable coverage per single roll for each pattern repeat, rounded up to whole double rolls. Change any number in the wallpaper calculator.

Frequently asked questions

Sources: Sherwin-Williams: how to estimate wallpaper, Selected Wallpapers: European rolls vs double rolls, Wallpaper Installer: wallpaper estimate. Read 7 November 2026.