Wallpaper Calculator
Walls totaling 40 ft, 8 ft high, with 3 ft of doors and 5 ft of windows removed, need 19 strips and 7 rolls of a 20.5 in by 33 ft roll when the pattern repeats every 21 in.
Last updated . Wall widths start at 40 ft. Height starts at 8 ft. The roll boxes start at 20.5 in, 33 ft, and a 21 in repeat, and those three are examples.
A wallpaper calculator that counts strips, not area. The strip grows to the next multiple of the pattern repeat, each roll contributes only whole strips, and the roll count rounds up.
Paint on the same walls: paint calculator. Sheets behind the paper: drywall calculator. Cladding outside: siding calculator.
Wallpaper rolls
20.5 in by 33 ft and a 21 in repeat are examples so the roll count can be checked. Measure the roll in your hand. A repeat of 0 means the strip is exactly the wall height. Door and window widths are removed from the sum of the wall widths before the strips are counted.
Results
How the rolls are counted
Net width = sum of the wall widths − door widths − window widths. The opening room is 40 − 3 − 5 = 32.00 ft. Those deductions are widths along the wall, not the square feet of the opening. A short door still removes its full width from the strip count, because a patterned strip is not usually cut and restarted under a head.
When the repeat is greater than zero, strip length = ceil(height ÷ repeat) × repeat. 8 ft and a 21 in repeat give 8.7500 ft. Strips per roll = floor(roll length ÷ strip length) = floor(33 ÷ 8.75) = 3. Strips needed = ceil(net width ÷ roll width) = ceil(32 ÷ (20.5 ÷ 12)) = 19. Rolls = ceil(19 ÷ 3) = 7. A repeat of 0 skips the match and sets the strip equal to the height, so the same roll holds 4 strips and the job drops to 5 rolls.
No brand’s roll is assumed. 20.5 in, 33 ft, and 21 in are examples in the fields. Replace them with the width, the length, and the pattern match printed on the roll. This count does not add a second waste percent on top of the rounding.
Roll counts for this room
| Case | Net width | Strip | Per roll | Strips | Rolls |
|---|---|---|---|---|---|
| 21 in repeat, doors 3 ft, windows 5 ft | 32.00 ft | 8.7500 ft | 3 | 19 | 7 |
| Repeat 0, same openings | 32.00 ft | 8.0000 ft | 4 | 19 | 5 |
| 21 in repeat, no openings | 40.00 ft | 8.7500 ft | 3 | 24 | 8 |
Worked example
Leave 40 ft of walls, 8 ft high, 3 ft of doors, 5 ft of windows, a 20.5 in roll, 33 ft long, repeating every 21 in. Rolls reads 7. Strips needed reads 19. Strips per roll reads 3.
Wallpaper questions
How many rolls cover 40 ft of walls at 8 ft with a 21 in repeat?
Leave walls at 40 ft, height at 8 ft, door widths at 3 ft, window widths at 5 ft, roll width at 20.5 in, roll length at 33 ft, and pattern repeat at 21 in. Net width reads 32.00 ft. Strip length reads 8.7500 ft · 105.00 in. Strips per roll reads 3. Strips needed reads 19. Rolls reads 7.
How does the repeat turn 8 ft into an 8.75 ft strip?
21 in is 1.75 ft. 8 ÷ 1.75 = 4.571, and that rounds up to 5 repeats. 5 × 1.75 = 8.75 ft, which prints as 8.7500 ft · 105.00 in. The extra 0.75 ft is the match allowance. If the height had already landed on a multiple of the repeat, the allowance would be zero.
Why 19 strips and 7 rolls?
Net width is 40 − 3 − 5 = 32 ft. The roll is 20.5 ÷ 12 = 1.708333 ft wide. 32 ÷ 1.708333 = 18.7317, which rounds up to 19 strips. A 33 ft roll holds floor(33 ÷ 8.75) = 3 full strips. 19 ÷ 3 = 6.333, which rounds up to 7 rolls. Leftover inches on the last strip of a roll are not spliced onto the next strip.
What if the pattern repeat is 0?
Set pattern repeat to 0 and leave the other opening values. Strip length reads 8.0000 ft · 96.00 in. Strips per roll reads 4, because floor(33 ÷ 8) = 4. Strips needed stays 19. Rolls reads 5. A zero repeat means the strip is the wall height, with no match allowance.
What if the doors and windows are left at zero?
Set door widths and window widths to 0. Put the repeat back to 21 in if you cleared it. Net width reads 40.00 ft. Strip length stays 8.7500 ft · 105.00 in. Strips per roll stays 3. Strips needed reads 24. Rolls reads 8. The deductions are widths, not areas, and they come off the wall-width sum before the strip count.
What if the roll is shorter than one strip?
Set roll length to 8 ft and leave height at 8 ft with the 21 in repeat. The strip is 8.75 ft, so the roll cannot hold one. Every result line reads —. The note reads: The roll is shorter than one strip, so it yields no full strip.
Are 20.5 in, 33 ft, and 21 in a standard roll?
No. Those three numbers are sitting in the boxes so this 7-roll example can be checked. Measure the roll you bought. If the door and window widths add up to the walls or more, the note reads: Door and window widths are at least as wide as the walls, so no strip remains.