Wallpaper Calculator

Calculate how many rolls of wallpaper you need for a room from the wall height, perimeter, roll size and pattern repeat, with strips per roll and strips needed.

By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: To estimate wallpaper, divide the room perimeter in inches by the roll width for the number of strips, divide the roll length by the wall height plus 4 in of trim for strips per roll, then divide strips by strips per roll. A 12 x 10 ft room with 8 ft walls, 1 door and 2 windows needs 24 strips of 20.5 in paper, which is 8 rolls of 33 ft.

Results

Rolls to buy: 8 rolls; 24 strips at 3 strips per roll
Strips needed: 24 strips; 26 strips of 20.5 in around the 44 ft perimeter, minus 2 for doors and windows
Strips per roll: 3; Each strip is 100 in long, including 4 in for trimming
Wall area: 302 sq ft; 8 rolls hold 451 sq ft before trimming and pattern matching

Wallpaper formula

Strips needed = Perimeter (in) / roll width, rounded up, minus 1 per door and 0.5 per window
Strip length (in) = Wall height x 12 + 4, rounded up to a whole pattern repeat
Strips per roll = Roll length (in) / Strip length, rounded down
Rolls = Strips needed / Strips per roll, rounded up

Worked example

A 14 x 12 ft bedroom with 9 ft walls, 2 doors, 2 windows and a 21 in wide, 33 ft roll with an 18 in repeat: the perimeter is 52 ft = 624 in. 624 / 21 = 29.7, so 30 strips, minus 2 for the doors and 1 for the two windows = 27 strips.

Strip length: 9 x 12 + 4 = 112 in, rounded up to whole 18 in repeats = 126 in. 33 ft = 396 in, and 396 / 126 = 3.1, so 3 strips per roll. 27 / 3 = 9 rolls.

Quick reference

Wallpaper for rooms with 8 ft walls (20.5 in x 33 ft rolls, no repeat, 1 door and 2 windows)
Room size	Perimeter	Strips	Rolls
10 x 10 ft	40 ft	22	8
10 x 12 ft	44 ft	24	8
12 x 12 ft	48 ft	27	9
12 x 14 ft	52 ft	29	10
14 x 16 ft	60 ft	34	12
15 x 20 ft	70 ft	39	13

How to calculate wallpaper

Wallpaper is hung in vertical strips, so count strips rather than square feet. Measure the room perimeter in inches and divide by the roll width to get the number of strips around the room. Each strip must be the wall height plus about 4 inches for trimming, and if the paper has a pattern repeat, each strip is cut to a whole number of repeats so the pattern lines up from strip to strip.

Divide the roll length by the strip length and round down for the strips you get per roll. With 8 foot walls and a 33 foot roll you get 3 full strips, and the 8 feet left over is only useful above doors and windows. Divide the strips needed by the strips per roll and round up to whole rolls.

Roll sizes, repeats and ordering

Almost all wallpaper now sold in the United States comes as a double roll, 20.5 or 21 inches wide by 33 feet long, even when the price is quoted per single roll. Wide American papers are 27 inches by 27 feet. Read the label for the exact width, length and pattern repeat before you calculate, because a 27 inch roll needs fewer strips but yields fewer strips per roll.

A drop-match pattern wastes more than a straight match, so use the full repeat when the label says half-drop. Order every roll at once and check that the run or dye lot numbers match, and keep one extra roll for repairs. Deduct a strip per door and half a strip per window; do not deduct for small windows if the paper has a large repeat.

Key facts

The most common roll today is 20.5 or 21 in wide by 33 ft long (52 cm x 10 m), sold as a double roll covering about 56 sq ft.
A wide American double roll is 27 in x 27 ft, about 60 sq ft; the single roll is 27 in x 13.5 ft.
After trimming and pattern matching, only about 70 to 80% of a roll ends up on the wall.
Allow 4 in extra per strip, 2 in at the top and 2 in at the bottom, for trimming.
Rolls with a large pattern repeat can waste 20 to 25% more paper than a plain or random-match design.

Frequently asked questions

How many rolls of wallpaper do I need for a 12x12 room?

With 8 foot walls, one door and two windows, the room needs 27 strips of 20.5 inch paper. At 3 strips per 33 foot roll that is 9 rolls.

How many square feet does a roll of wallpaper cover?

A 20.5 in x 33 ft double roll holds about 56 square feet, but after trimming and matching you can count on about 42 square feet on the wall. A 27 in x 27 ft American double roll holds 60 square feet.

What is a pattern repeat and how does it change the amount?

The repeat is the vertical distance before the design starts over. Each strip is cut to a whole number of repeats so adjacent strips line up, which lengthens each strip and can reduce the strips per roll from 3 to 2 on tall walls.

Should I deduct doors and windows?

Deduct one strip per door and half a strip per window. Wallpaper still has to run above and below windows, so deducting their full area would leave you short.

Sources and references

How to estimate wallcovering rolls for a room (Wallcoverings Association)
Wallpaper specifications: roll widths, lengths, coverage and pattern match (Brewster Home Fashions)
How to measure and cut wallpaper strips (Brewster Home Fashions)

Next steps for this project

The usual order for a paint & walls project. See all paint & walls calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.