Wallpaper Calculator

Enter the walls and the real width and length of your wallpaper to estimate the number of rolls, counted strip by strip.

Total width of the walls to cover (add up the walls)

Height of the wall (the part to cover)

Width of the wallpaper (varies by product)

Length of one roll as sold (varies by product)

Extra length per strip for pattern repeat and trimming (empty = 0)

Add the length needed to match the pattern repeat to the trimming allowance at the top and bottom, and enter the total. Wallpaper without a pattern repeat is 0.

Spare strips (empty = 0)

strips

Strips to cover mistakes, the areas around windows and doors, and corners. They are added before the number of rolls is worked out.

Rolls needed —

Details
Strips needed (from the wall width)	—
Strips needed (including spares)	—
Length of one strip	—
Strips that can be cut from one roll	—
Strips used from the last roll	—
Left over on the last roll	—
Left over on all rolls	—

This counts strips, not area. It does not subtract windows or doors, does not plan pattern matching beyond the extra length you enter, and does not allow for overlap or the condition of the wall. Offcuts at the end of a roll are not reused for the next strip. The result can differ from an area-based estimate.

The number copied is the number of rolls.

How it is calculated

Wallpaper goes up in strips of a fixed width, cut to the height of the wall. So the tool counts strips instead of dividing by area.

Strips needed = total wall width ÷ paper width, rounded up.
Length of one strip = wall height + the extra length for pattern repeat and trimming.
Strips from one roll = roll length ÷ length of one strip, rounded down. A strip is not joined in the middle of a roll.
Rolls needed = (strips + spare strips) ÷ strips from one roll, rounded up.

If one strip is longer than a whole roll, no strip can be cut and the tool shows an error. Every size is converted exactly from its own unit (1 ft = 0.3048 m, 1 in = 0.0254 m, 1 yd = 0.9144 m).

Enter the real size of your roll

Roll sizes differ by country, brand and product, and a "single roll" or a "double roll" is not a fixed size everywhere. This tool does not assume any roll size. Enter the width and the length of the roll as it is sold, as printed on the label or in the product information, and the number of rolls comes out in that same unit of sale.

Area-based estimates are different

Many online estimates divide the wall area by the area of a roll. This tool counts whole strips, which usually needs more wallpaper because each strip is cut to the wall height and the leftover at the end of a roll is not reused. The two methods can give different answers.

Example

Walls totaling 40 ft, a height of 8 ft, paper 20.5 in wide, a roll length of 33 ft, and 4 in extra per strip (example values only; use the numbers for your product):

Strips: 40 ft = 480 in; 480 ÷ 20.5 = 23.41 → 24 strips
Length of one strip: 8 ft + 4 in = about 8.333 ft
Strips from one roll: 33 ÷ 8.333 = 3.96 → 3 strips
Rolls: 24 ÷ 3 = 8 rolls

What is not included

Windows, doors and other openings are not subtracted. Reduce the total wall width yourself if you leave an area uncovered, or add spare strips for waste.
Pattern matching is covered only by the extra length you enter. The offset of drop patterns, overlap, and the wall's condition are not calculated.
Rolls sold in different lots can differ in color; buy all the rolls at the same time.

Sources

The length definitions come from NIST SP 811 Appendix B.8 and B.9 (foot, inch and yard rows read word for word), checked on November 1, 2026. The roll-counting method is a general calculation, not taken from a source. Roll sizes of products were not checked, and none is assumed.

Frequently asked questions

How many rolls of wallpaper do I need?

It depends on the wall width and height, and on the width and length of your roll. Enter them above. The tool counts strips.

Does the tool use a standard roll size?

No. Enter the width and length of the roll as sold.

Why is the answer different from an area calculator?

This tool counts whole strips and does not reuse the offcut at the end of a roll, so it often needs more.

Does it subtract windows and doors?

No. It is a simple estimate; use spare strips or reduce the wall width yourself.