Wallpaper Calculator

How Many Rolls of Wallpaper Do I Need?

Wallpaper Formula

Formula

\[ L_{eff} = L - \frac{O}{H}, \quad l_{cut} = \left\lceil \frac{H\left(1 + \frac{W}{100}\right)}{R_p} \right\rceil \cdot R_p \\ N_s = \left\lceil \frac{L_{eff}}{W_r} \right\rceil, \quad S_r = \left\lfloor \frac{L_r}{l_{cut}} \right\rfloor, \quad N_r = \left\lceil \frac{N_s}{S_r} \right\rceil \]

Where:

\(L\) — total wall length, i.e. the room perimeter (m)
\(H\) — wall height (m)
\(O\) — total area of openings such as doors and windows (m²)
\(R_p\) — vertical pattern repeat (m); 0 for plain wallpaper
\(W\) — waste allowance (%)
\(L_r\) — usable length of one roll (m)
\(W_r\) — roll width (m)
\(N_s\) — number of strips needed
\(S_r\) — strips cut from one roll
\(N_r\) — rolls to buy

The openings are converted into an equivalent wall length (area divided by height) and subtracted from the perimeter. Each strip is cut to the wall height plus waste, rounded up to a whole pattern repeat so the design matches across strips.

Wallpaper – Calculation Example

Example: a room with a total wall length of 14 m, a wall height of 2.5 m and 6 m² of door and window openings. The rolls are 10 m long and 53 cm wide, the wallpaper is plain (pattern repeat 0) and the waste allowance is 10%.

\[ L_{eff} = 14 - \frac{6}{2.5} = 14 - 2.4 = 11.6 \text{ m} \]

\[ l_{cut} = 2.5 \times 1.10 = 2.75 \text{ m} \]

\[ N_s = \left\lceil \frac{11.6}{0.53} \right\rceil = 22 \text{ strips}, \quad S_r = \left\lfloor \frac{10}{2.75} \right\rfloor = 3 \text{ strips/roll} \]

\[ N_r = \left\lceil \frac{22}{3} \right\rceil = 8 \text{ rolls} \]

Result: you need 22 strips, get 3 strips per roll, and should buy 8 rolls of wallpaper.

How to Use the Wallpaper Calculator

Measure the Total wall length: add up the length of every wall you plan to cover (the room perimeter) and enter it with the unit selected (m or ft).
Enter the Wall height from floor to ceiling (or to the point where the wallpaper will stop). Use the same unit as for the wall length.
Add the combined Openings area you do not want to cover. A rough guide: one door ≈ 2 m², one window ≈ 1.5 m².
Check the wallpaper label and enter the Roll length and Roll width. Standard European rolls are 10.05 m long and 53 cm wide; American rolls are often 27 in wide.
Enter the Pattern repeat — the vertical distance at which the design repeats. Enter 0 for plain wallpaper. The repeat is usually printed on the label.
Set the Waste allowance (default 10%). This covers trimming at the ceiling and skirting board, offcuts and mistakes.
Read the results: Wallpaper strips needed, Strips per roll and Rolls to buy.

How Wallpaper Estimation Works

Wallpaper is hung in vertical strips of one roll width. The calculator first works out how much wall actually needs covering: the total wall length minus the width taken up by doors and windows (their area divided by the wall height). It then divides that effective length by the roll width to find the number of strips, rounding up because you cannot hang half a strip.

Next it determines how many full strips can be cut from a single roll. Each strip must be slightly longer than the wall height — the extra covers the waste allowance. If the wallpaper has a pattern, the cut length is rounded up to a whole multiple of the pattern repeat, otherwise adjacent strips would not match at the seams. The number of rolls is finally the total strips divided by the strips per roll, rounded up to a whole roll.

The pattern repeat has a big impact: a large repeat wastes a lot of each roll because every strip must start at the same point in the design. A 64 cm repeat on a 2.5 m wall can add a full extra roll to a medium room compared with plain paper. If the calculated cut length exceeds the roll length, the roll is too short for your wall and the calculator will tell you so.

Assumptions, Limitations and Practical Tips

Deducting openings is a simplification. Openings are subtracted by average width, which assumes they are spread along the wall. Strips above doors and windows still use full-length pieces, so a very large window may need more paper than calculated. Keeping a full roll spare is a cheap insurance.
Pattern matching direction matters. The calculator assumes the pattern repeat is a straight match. Some wallpapers have a drop (offset) match, where alternate strips are shifted by half a repeat — the repeat length on the label already accounts for this, so entering it as given is correct.
Buy from the same batch. Roll labels show a batch or lot number; colors can differ slightly between batches. Always buy all rolls at once and check the batch numbers match.
Keep one roll spare. Leftover wallpaper is invaluable for future repairs. Many suppliers accept unopened rolls back, and having 5–10% extra is standard practice in professional decorating.
Old or uneven walls may need lining paper underneath and a higher waste allowance (15–20%), because strips are trimmed to fit irregular corners.
Check the usable roll length. Some labels quote the total length, but a few centimetres at each end may be damaged. Enter the usable length to be safe.

If you are planning a wider room makeover, you might also find our Laundry Load Weight Calculator and Long-Term Food Storage Calculator useful for other household planning tasks.

Frequently Asked Questions

How do I calculate wallpaper by hand without a calculator?

Divide the room perimeter by the roll width to get the number of strips, rounding up. Then divide the roll length by the cut length per strip (wall height plus about 10%) to see how many strips one roll gives. Finally divide strips needed by strips per roll, rounding up to whole rolls. Example: a 14 m perimeter with 0.53 m wide rolls needs \( \lceil 14 / 0.53 \rceil = 27 \) strips.

How many rolls of wallpaper do I need for an average room?

A typical 3 m × 4 m bedroom with 2.5 m ceilings needs about 5–7 standard rolls (10.05 m × 53 cm) for plain paper, and 1–2 more if the wallpaper has a large pattern repeat. A larger living room of 5 m × 4 m usually takes 8–10 rolls. Always run the numbers for your actual room, and consider buying one extra roll for repairs.

What is pattern repeat and how does it affect the number of rolls?

Pattern repeat is the vertical distance at which the printed design repeats itself. When matching patterns at the seams, each strip must be cut long enough to start at the same point of the design, so the cut length is rounded up to a whole multiple of the repeat. A large repeat, such as 64 cm, can waste 30–40% of each roll and typically adds one or two extra rolls to a medium room.

Should I deduct doors and windows from my wallpaper calculation?

Deducting openings is a reasonable simplification, but it slightly underestimates the need. Strips above doors and windows still require full-height pieces, so openings cannot always be skipped. Deduct roughly half to two-thirds of the actual opening area for a safer estimate, or deduct nothing and simply keep the leftover as your spare roll.

What are standard wallpaper roll sizes in different countries?

European standard rolls are 10.05 m long and 53 cm wide. American rolls are typically 27 in (68.6 cm) wide, and double rolls in the US are commonly 33 ft (10.05 m) long. Metric rolls sold as 5 m or 15 m lengths also exist. Conversions: 1 ft = 0.3048 m, 1 in = 2.54 cm, 1 m² ≈ 10.76 ft². Always check your actual label rather than assuming a standard size.

What waste allowance should I use for wallpaper?

10% is a good default for flat, even walls with plain paper. Use 15–20% for older or uneven walls, corners that are not square, first-time hanging, or a large pattern repeat — the rounding to a whole repeat already adds waste, so the two effects compound. For plain wallpaper on a perfectly rectangular room, 5–10% is usually enough.

Why do I need rolls from the same batch or lot number?

Wallpaper is printed in batches, and the color or pattern alignment can vary slightly between production runs. If you mix batches, adjacent strips may show a visible shade difference at the seams. When buying, check that every roll carries the same batch number printed on the label; if you need more later, the same batch may no longer be available.