How to use the wallpaper calculator
Choose One wall for an accent wall or Whole room for four walls at the top. You can add or remove walls afterward, up to eight, which covers a room with a bay or an alcove.
Next, set the roll size. A US double roll is about 20.5 inches wide and 33 feet long. A metric roll is about 0.53 meters wide and 10 meters long. The label on the roll gives the exact size, and some papers come wider or longer, so check it.
Then set the pattern match and the repeat, both printed on the label:
- Straight: the design lines up straight across every strip.
- Half-drop: every other strip starts half a repeat lower.
- Free match: stripes, textures and grasscloth with nothing to line up.
Enter the wall height, then the width of each wall and the doors and windows on it. Tap through the walls with the tabs.
The drawing papers your walls strip by strip from the left corner. Each seam is marked, and the pale tail above the ceiling line is the paper you cut off each strip. Watch it grow as you raise the repeat. Save the drawing as an image to bring to the store.
The rules behind the count
Count strips, not square feet. Paper goes up in vertical strips the width of the roll. A 12 foot wall is 144 inches wide, and 144 divided by 20.5 is just over 7, so it takes 8 strips. You can’t hang 7 and a bit.
Add trim to every strip. Each strip is cut about 2 inches long at the top and 2 inches at the bottom, then trimmed to fit. That is 4 inches on every strip.
Round up to the repeat. Each strip has to start at the same point in the pattern as the one beside it. So the cut length is the wall height plus trim, rounded up to a whole number of repeats. An 8 foot wall plus 4 inches of trim is 100 inches. With a 21 inch repeat, that rounds up to 105 inches, five whole repeats.
Half-drops take half a repeat more. Every other strip starts half a repeat lower, so each strip uses about half a repeat more paper.
Fill the rolls. A 33 foot roll is 396 inches. At 105 inches per strip it gives 3 strips, with 81 inches left over. Short pieces above doors and below windows can come from those leftovers, so the calculator packs them onto leftover ends before it opens a new roll.
Buy one more. Paper is printed in batches that can differ slightly in color. One spare roll from the same batch covers a miscut and future repairs.
Assumptions
Walls are plain rectangles of the same height, papered from the floor or baseboard to the ceiling. Doors are 36 by 80 inches and windows 36 by 48 inches, spread evenly along each wall. Strips are hung from the left corner of each wall, so a door or window only saves paper where it covers the full width of a strip. Corners are not wrapped, and each wall starts with a fresh strip.
The count uses the trim and repeat rules on the most common labels. Some papers, especially murals and panels, are sold by the drop or by the set instead of by the roll. Follow the maker’s guide for those. Ceilings, sloped walls and stairwells are not modeled.
Worked example
Say you are papering a whole 14 by 12 foot room with 8 foot walls. There is one door, and three windows spread over two walls. The paper is a US double roll with a 21 inch straight repeat.
- Strips: the two 14 foot walls take 9 strips each and the two 12 foot walls take 8 each. That is 34 strips.
- Cut length: 96 inches of wall plus 4 inches of trim is 100 inches, rounded up to five repeats, so 105 inches per strip. Each strip wastes 9 inches.
- Strips per roll: 396 inches divided by 105 is 3.77, so 3 strips per roll.
- Rolls: 34 strips at 3 per roll would be 12 rolls. Three strips fall fully across a window, so they are cut into a short piece above and a piece below. Those short pieces fit on the leftover roll ends, and the total comes to 11 double rolls, plus one spare.
Switch to a half-drop and each strip grows to 115.5 inches. That still fits 3 strips per roll, so the count stays at 11.
Pin it for later
Wallpaper Calculator FAQ
How many rolls of wallpaper do I need for a 12 foot wall?
A 12 ft wide, 8 ft tall wall takes 8 strips of US double-roll paper, which is about 20.5 in wide. With a 21 in pattern repeat each strip is cut 105 in long, so a 33 ft roll gives 3 strips. That makes 3 double rolls, plus one spare.
What does pattern repeat mean on wallpaper?
The repeat is the distance down the roll before the design starts over. Each strip has to start at the same point in the pattern as its neighbor, so the cut length is rounded up to whole repeats. A bigger repeat means more paper wasted per strip.
What is the difference between straight match and half-drop?
With a straight match the design lines up straight across from one strip to the next. With a half-drop, every other strip is shifted down by half a repeat, so the motif steps diagonally across the wall. Half-drop papers usually use a little more paper.
Should I subtract doors and windows when buying wallpaper?
Only partly. A door or window saves paper only where it covers the full width of a strip, and even then you still need short pieces above and below it. The calculator works this out strip by strip, so it only takes off what a strip really saves.
Why should I buy an extra roll of wallpaper?
Wallpaper is printed in batches, and the color can shift slightly from one batch to the next. One extra roll from the same batch covers a miscut strip, a hard corner or a repair later on.