Wallpaper Roll Calculator
Drops and rolls from perimeter, height and pattern repeat.
Quick answer
With the default inputs: Room perimeter 18 · Wall height 2.8 · Roll length 10 etc.Rolls needed 12 rolls
Edit the inputs below to recalculate.Inputs
Result
Rolls needed
12rolls
| Net wall area | 50.4m² |
| Drops needed | 34drops |
| Cut length per drop | 3.12m |
| Drops per roll | 3drops |
| Coverage width | 18.0m |
| Total length bought | 120.0m |
| Paper per m² | 1.26m²/m² |
Each drop must include a full pattern repeat, otherwise the pattern will not align. With a 1.06 m repeat a roll may yield only two drops, wasting up to 30% — calculate before buying.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Cut length | L = wall height + pattern repeat (0.1 m trim if plain) |
| Drops per roll | n = floor(roll length ÷ L) |
| Drops needed | N = ceil(perimeter ÷ roll width) |
| Rolls | R = ceil(N ÷ n) |
An 18 m perimeter at 2.8 m with 0.53 × 10 m rolls and no repeat: 2.90 m per drop, 3 drops per roll, 34 drops, so 12 rolls. At a 0.64 m repeat each drop is 3.44 m, only 2 fit per roll, and 17 rolls are needed.
How to work it out
- Count drops first: perimeter divided by roll width, rounded up. Wallpaper is hung in drops, and this line is the whole method.
- Work out the cut length per drop: ceiling height plus the pattern repeat (a 0.32 m repeat adds 0.32 m, not half), plus 50 mm top and bottom for trimming.
- Work out drops per roll: roll length divided by drop length, rounded down. A 10 m roll at 3.12 m per drop gives three drops and 0.64 m of waste.
- Rolls = drops ÷ drops per roll, rounded up. Divide drops by drops, never area by area.
- Do not deduct openings. Paper runs above and below a window and a single drop usually spans it, so deducting area undercounts.
Where it goes wrong
- Dividing area to get rolls — a 0.53 × 10 m roll is labelled 5.3 m²; an 18 m perimeter at 2.8 m works out at three rolls by area but needs five, a 40% shortfall.
- Adding half the repeat — only half-drop matching takes half; a straight match aligns full repeats and adding half puts every seam out of register.
- Deducting window and door area — paper still goes above and below, and drops cross the opening, so the deduction loses paper outright.
- Buying one room in two purchases — wallpaper shows shade variation far more than tiles; a different dye lot on one wall is obvious.
Material and cost
Non-woven 60-200 CNY per roll, paper 100-300, imported 300-800. Labour 15-25 CNY/m² or 40-80 per roll. Primer and adhesive 5-10 CNY/m².
On site
- Prime the wall first. Hanging straight onto skim means the skim comes away with the paper when it is stripped.
- Number the cut drops and hang them in order, or the pattern will step across the wall.
- Avoid seams on external corners: start the drop at the corner and wrap 20 mm around it so the joint sits in a re-entrant corner instead.
Basis
- GB 50210-2018 Code for acceptance of building decoration, Chapter 9 (wallcovering)
- GB 18585-2001 Limit of harmful substances in wallpaper for interior decoration
FAQ
Why does a pattern repeat cost so much extra?
With a repeat every drop must start at the same point in the pattern: a 2.8 m wall plus a 0.64 m repeat is 3.44 m, so a 10 m roll yields two drops and leaves 3.12 m unusable. That is why large repeats waste so much. Calculate with this formula rather than dividing area, or you will run short.
Can I deduct doors and windows?
Rarely, because paper is hung in full drops: the strips above and below an opening are cut from a full drop and the offcut seldom matches elsewhere. You only save when a door runs full height or a window sits exactly between two drops. This tool shows net area but does not reduce the roll count.
How much adhesive?
About 1 kg of powder, once mixed, covers 20-25 m², or 0.3-0.4 kg per 5.3 m² roll. Primer is separate at roughly 8-10 m² per kg. Prime the wall first: adhesive soaked straight into the filler coat will fail in sheets later.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Wallpaper Roll Calculator. 2026-10-25. https://jianzhujisuan.com/en/wallpaper
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.