Quick answer
Strips = ⌈perimeter ÷ roll width⌉, and rolls = ⌈strips ÷ strips per roll⌉, where a roll yields ⌊roll length ÷ strip length⌋ strips. Covering 40 ft with 20.5 inch rolls 33 ft long and 8 ft strips needs 24 strips, 4 per roll, so 6 rolls.
Enter the wall length, height, roll width and length. The calculator returns rolls and strips. Use this wallpaper calculator to check your own figures.
Related tools: Plywood Calculator: Sheets of plywood or OSB for an area. Drywall Calculator: Sheets of drywall for walls after deducting openings. Roof Pitch Calculator: Roof pitch as rise per 12 inches, angle, slope percent and rafter length factor.
How to use the Wallpaper Calculator
- Enter wall length to cover (perimeter) (ft) (above 0).
- Enter wall height (ft) (above 0).
- Enter roll width (in) (above 0).
- Enter roll length (ft) (above 0).
- Optionally, enter pattern repeat (optional) (in) (0 or more).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Wall length to cover (perimeter) | A number, in ft | > 0 |
| Wall height | A number, in ft | > 0 |
| Roll width | A number, in in | > 0 |
| Roll length | A number, in ft | > 0 |
| Pattern repeat (optional) (optional) | A number, in in | ≥ 0 |
Formula and method
Formula
strips = ⌈perimeter ÷ roll width⌉; strip length = height rounded up to the repeat; rolls = ⌈strips ÷ ⌊roll length ÷ strip length⌋⌉
IEEE-754 double precision; shown to the decimals indicated.
Does not subtract windows and doors, which makes the result slightly generous. Plan geometry only; confirm quantities with your supplier and local code before ordering.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Wall length to cover (perimeter) = 40; Wall height = 8; Roll width = 20.5; Roll length = 33.
| Result | Value |
|---|---|
| Rolls needed | 6 |
| Strips needed | 24 |
| Strips per roll | 4 |
Example 2
Inputs: Wall length to cover (perimeter) = 56; Wall height = 9; Roll width = 21; Roll length = 33; Pattern repeat (optional) = 12.
| Result | Value |
|---|---|
| Rolls needed | 11 |
| Strips needed | 32 |
| Strips per roll | 3 |
Example 3
Inputs: Wall length to cover (perimeter) = 30; Wall height = 8; Roll width = 27; Roll length = 27.
| Result | Value |
|---|---|
| Rolls needed | 5 |
| Strips needed | 14 |
| Strips per roll | 3 |
The first line is the headline result (rolls needed). Below it the wallpaper Calculator lists strips needed and strips per roll, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
The count
480 inches ÷ 20.5 = 23.4, rounded up to 24 strips. A 33 ft roll gives 4 strips of 8 ft (32 ft), so 24 ÷ 4 = 6 rolls.
Pattern repeat
Patterned paper wastes length matching the repeat, so strip length is rounded up to the repeat. Order all rolls from the same batch, and add one for mistakes. Openings are not deducted.
How the result changes with wall length to cover
Holding every other input at the first worked example, this table changes only wall length to cover. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Wall length to cover | Rolls needed | Strips needed | Strips per roll |
|---|---|---|---|
| 20 | 3 | 12 | 4 |
| 40 | 6 | 24 | 4 |
| 80 | 12 | 47 | 4 |
| 160 | 24 | 94 | 4 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Roll length: entering "5" shows "The roll is shorter than one strip." beside that field and no result.
- Wall length to cover (perimeter): entering "0" shows "Wall length to cover (perimeter) must be greater than 0." beside that field and no result.
Choosing between the Wallpaper Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Plywood Calculator](/construction/plywood-calculator/) | area to cover, sheet size and waste allowance | Sheets needed |
| [Drywall Calculator](/construction/drywall-calculator/) | total wall length, wall height and sheet size | Sheets needed |
| [Roof Pitch Calculator](/construction/roof-pitch-calculator/) | i know the and value | Pitch |
| [Tile Calculator](/construction/tile-calculator/) | area to tile, tile length and tile width | Tiles needed |
| [Aquarium Volume Calculator](/construction/aquarium-volume/) | length, width and water height | Capacity |
Background: construction estimates
Material quantities are geometry plus a margin. Calculate the exact volume or area, add an allowance for waste, spillage, cuts and uneven ground (calculator pages commonly mention 5 to 10 percent, a rule of thumb that varies by material and job) and round up to whole units. One cubic yard is exactly 27 cubic feet.
Suppliers often have minimum order sizes and may charge for small loads, so confirm quantities, product yields and local code with your supplier or a qualified estimator before ordering.
Assumptions and limitations
- Roll must be long enough for one strip
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for roll length and wall length to cover (perimeter) to confirm this.
Frequently asked questions
What is a pattern repeat?
The vertical distance before the pattern repeats.
Do I subtract doors?
Not usually; windows can be subtracted.
What about double rolls?
Enter the length of the roll as sold.
What does the Wallpaper Calculator calculate?
Rolls of wallpaper from room perimeter, height and pattern repeat. It returns Rolls needed, Strips needed and Strips per roll.
What formula does the Wallpaper Calculator use?
strips = ⌈perimeter ÷ roll width⌉; strip length = height rounded up to the repeat; rolls = ⌈strips ÷ ⌊roll length ÷ strip length⌋⌉. Does not subtract windows and doors, which makes the result slightly generous.
What do I need to enter in the wallpaper Calculator?
You enter Wall length to cover (perimeter) (ft), Wall height (ft), Roll width (in) and Roll length (ft). Optional: Pattern repeat (optional) (in).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Roll must be long enough for one strip.
What is an example of a wallpaper result?
With wall length to cover (perimeter) 40, wall height 8, roll width 20.5 and roll length 33, the rolls needed is 6.
Can I rely on this calculator for a decision?
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work. For this calculator in particular: Roll must be long enough for one strip.
Related calculators
- Plywood Calculator — Sheets of plywood or OSB for an area.
- Drywall Calculator — Sheets of drywall for walls after deducting openings.
- Roof Pitch Calculator — Roof pitch as rise per 12 inches, angle, slope percent and rafter length factor.
- Tile Calculator — Number of tiles (and boxes) for an area.
- Aquarium Volume Calculator — Capacity and filled weight of a rectangular aquarium.
- Flooring Calculator — Flooring area with waste, and boxes if you know the coverage per box.
Sources
- OpenStax, Prealgebra 2e (Rice University): perimeter, area, volume, circumference and the Pythagorean theorem
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B conversion factors (international foot 0.3048 m, inch 25.4 mm, US gallon 3.785411784 L)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.