Wallpaper Calculator
How many rolls a room needs — wall width, height, roll size and pattern repeat included, the way decorators count.
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How It's Calculated
Wallpaper is hung in vertical strips, not measured as flat area, and that single fact drives the whole calculation. The number of strips needed is total wall width ÷ roll width, rounded up since a partial strip still consumes a full width of paper. How many strips come out of one roll is roll length ÷ strip length, rounded down — a leftover shorter than one strip is wasted. Required rolls = strips needed ÷ strips per roll, rounded up again.
The strip length itself is not just the wall height: add roughly 10 cm of trim allowance for the top and bottom cuts. If the paper has a pattern repeat — the vertical distance after which the printed motif repeats — every strip must start at the same point in the pattern so that adjacent strips line up, which forces the usable strip length to round up to the next whole multiple of the repeat. That rounding is where paper is lost: a small repeat wastes very little, but a large repeat can waste most of a strip's length on every single cut.
Take a concrete example: a 10 m long wall, 2.5 m high, papered with a standard 53 cm × 10.05 m roll and no pattern repeat. Strips needed = 1000 cm ÷ 53 cm ≈ 19 strips. Strip length = 250 cm + 10 cm trim = 260 cm, and one roll (1005 cm long) yields 1005 ÷ 260 ≈ 3 strips per roll. Rolls required = 19 ÷ 3 ≈ 7 rolls. Now introduce a 64 cm pattern repeat: the strip length must round up to the next multiple of 64 cm above 260 cm, which is 320 cm — each roll now yields only 1005 ÷ 320 ≈ 3 strips still, but the waste per strip rises sharply, and larger repeats or taller walls can drop the strips-per-roll count entirely, pushing the total to 10 rolls for the same wall.
What You Should Know
- Doors and windows are usually NOT subtracted from the wall area by professional decorators — the offcuts around openings rarely fit anywhere else on the job, and having spare strips from the same dye lot for future repairs is worth more than the small paper saving.
- Dye lots differ visibly even for the "same" wallpaper — order the full quantity in one purchase and check that every roll's label carries the identical batch number before hanging.
- Larger pattern repeats always increase waste, sometimes substantially — a 64 cm repeat can push the total roll count 30-40% higher than a plain, repeat-free paper on an identical wall.
- Buy at least one extra roll beyond the calculated total on any real job — cutting mistakes, corners, and awkward wall features consume paper that a pure area calculation cannot anticipate.
- Roll dimensions vary by market — European rolls commonly run 53 cm × 10.05 m, while American rolls (double or triple rolls) come in different widths and lengths, so always check the label before calculating.
Frequently Asked Questions
What do "straight match" and "offset match" mean?
Straight match repeats the pattern at the same height on every strip, so adjacent strips align directly. Offset (drop) match shifts the pattern half a repeat sideways between neighboring strips, which typically wastes a bit more paper. For offset patterns, enter the full repeat value — the calculation stays on the safe side.
Should I really not subtract doors and windows?
For a normal room, no — professional decorators intentionally skip that subtraction because the resulting safety margin covers cutting mistakes and provides matching spare paper for future repairs from the same dye lot. Only subtract manually for a genuinely dominant opening, like a full glass wall.
Why does a bigger pattern repeat mean more rolls?
Because each strip must start at the same point in the motif, the usable strip length has to round up to the next whole multiple of the repeat distance. A large repeat forces more rounding waste per strip than a small one, so the same wall needs noticeably more rolls purely because of the pattern, not the wall size.
How much extra should I order beyond the calculated total?
At least one full roll beyond the calculated figure is standard practice, more for rooms with many corners, alcoves or a steep pattern repeat. It is far cheaper to have one unused roll from the correct dye lot than to reorder later and receive a visibly different batch.
Do American and European rolls use the same math?
The formula is identical, but the numbers differ — European single rolls are typically 53 cm wide by about 10.05 m long, while American paper is often sold in double or triple roll bolts with different coverage per unit. Always enter the actual roll width and length from the label rather than assuming a standard size.
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