Wallpaper Calculator

Rolls, not square metres

Wallpaper is sold by the roll, priced per roll, and planned per wall — which is why area maths alone undercounts rooms. This page starts from the perimeter (the wall length you actually walk around), multiplies by height, subtracts the standard allowances for one door and one window, divides by the roll's area, and rounds up to whole rolls. The exclusions matter: a door's 1.8 m² and a window's 1.5 m² are usually wrapped in offcuts too awkward to reuse, so they leave the count rather than padding it.

Two roll sizes dominate: the standard 10 m × 53 cm roll (5.3 m²) and wider or longer designer rolls. Whatever your roll's label says, the tool takes its length and width and computes the area — the one input worth reading the label for.

A worked example, step by step

Problem: a bedroom with a 14 m perimeter and 2.5 m walls, one door, one window, standard 10 m × 53 cm rolls.

1. Plain wall area: 14 × 2.5 = 35 m².
2. Exclusions: door 1.8 + window 1.5 = 3.3 m².
3. Paperable area: 35 − 3.3 = 31.7 m².
4. Roll area: 10 × 0.53 = 5.3 m².
5. Rolls: 31.7 ÷ 5.3 = 5.98 → 6 rolls.

The near-miss in the last step is the reason rounding-up matters: 5.98 rounds to 6, but the panel computing a plain 35 m² room gets 35 ÷ 5.3 = 6.60 → 7 rolls. Three square metres of openings saved one roll here — on a larger room they save two, and that difference is the whole business case for measuring perimeter rather than guessing.

Roll sizes, side by side

Wider rolls mean fewer seams, which some patterned papers reward and some small rooms punish (harder handling around reveals). The price per square metre is the honest comparator only when seam count does not matter to your pattern.

Pattern repeat: the honest caveat

Every roll drawn from a patterned paper loses length to matching: each drop must line up with the next, so a 26 cm repeat wastes up to that much per drop. The panel's estimate does not model repeats — it is the plain-area answer — so the rule of thumb is: large repeats (25 cm+) add one roll to the tool's answer for a typical bedroom-size job, small repeats (5 cm or less) usually do not. Batch numbers matter too: paper printed in different dye lots differs visibly, so keep the batch on one wall consistent — one more reason to over-order by a roll rather than under-order.

Mistakes that quietly halve a hall

• Measuring wall length at the skirting only. Recesses, alcoves and chimney breasts bend the perimeter; walk it with a tape, don't read a floor plan.
• Ignoring pattern repeat. A large-repeat paper measured like plain paper lands one roll short, mid-wall.
• Ordering by a remembered label. Roll lengths doubled at some point in history; a 20 m double roll is two standard rolls in one, and the tool takes whichever length and width you enter.
• Excluding door and window twice. The subtraction is per opening, not per wall — a double aspect room has two windows; the panel's fields take counts.

Keep exploring

• Paint Quantity Calculator — the same room with a wet finish instead: coverage per litre.
• Tile Calculator — the wet-zone alternative for the wall around a basin.
• Length Converter — perimeter arithmetic, one wall at a time.
• Guide: Unit Conversion Mistakes to Avoid.