Wallpaper calculator
How many rolls a room needs — with the pattern repeat that drives the number up.
Calculator
Detailed breakdown
| Item | Quantity |
|---|
How to use this calculator
Measure
Measure the room in feet and enter the pattern repeat from the wallpaper label. Zero for a plain or random-match paper.
Calculate
Once you hit calculate, results update as you type. Change any number to compare options instantly.
Order
Print the estimate and take it to your supplier. Quantities are rounded up so you don't come up short.
Rolls are counted in strips, not square feet
Wallpaper is the one material where square footage will mislead you. Paper hangs in full-height strips, and a strip cannot span two rolls — so what you actually count is how many strips the room needs and how many whole strips come out of a roll.
Take a 12 by 15 foot room with 8 foot ceilings. The perimeter is 54 feet, and at a standard 20.5 inch roll width that is 32 strips. Each strip needs the 96 inch ceiling height plus about 4 inches of trim allowance, so 100 inches. A 33 foot roll is 396 inches, which yields 3 whole strips — the remaining 96 inches is scrap. Thirty-two strips at three per roll means 11 rolls.
So 25 percent of every roll is waste, and that's with a plain paper. A pattern repeat makes it worse, because every strip has to start at the same point in the design: you cut each strip to a whole number of repeats, not to the wall height. What surprises people is that the effect is a step, not a slope. In this room a repeat of 21 inches still gives 11 rolls — the extra length disappears into scrap you were already throwing away — but a 45 inch repeat drops you to two strips per roll and 16 rolls, while a 50 inch repeat goes back to 11. Run your actual repeat through the calculator rather than assuming a bigger one always costs more.
Doors and windows don't come out of the strip count. In practice you hang a full strip over an opening and trim it out afterward — the paper above and below a window still has to come from somewhere. And buy every roll in one batch or run number: dye lots differ visibly, and a mid-job reorder from a different batch shows as a stripe down the wall.
Frequently asked questions
How many rolls of wallpaper for a 12 by 15 room?
About 11 double rolls for an 8 foot ceiling with a plain paper. Some pattern repeats push it to 16, but not all large ones do — it depends on whether the rounded-up strip length still divides into the roll.
How does pattern repeat affect wallpaper quantity?
Each strip is cut to a whole number of repeats rather than to the wall height, so the strip gets longer and fewer of them come out of a roll. The jump is a step: the count only changes when the longer strip drops the strips-per-roll from three to two.
What is a double roll of wallpaper?
The US standard is about 20.5 inches wide by 33 feet long. It's sold as a double roll because a single roll rarely yields enough full strips to be practical.
Should I subtract doors and windows from wallpaper?
Not from the strip count. You hang a full strip over the opening and trim it, because the paper above and below still has to be covered and pattern-matched.
Why does wallpaper need the same batch number?
Dye lots vary between production runs. Paper from a different batch reads as a visible color change down the wall, so buy the whole job at once.
Where do I find the pattern repeat?
On the roll label or the sample book, usually given in inches alongside the match type. A straight match repeats level across the seam; a drop match staggers it and wastes more. If the label says random match, enter zero.
Sources
Formulas and material assumptions on this page follow published industry guidance: