Wallpaper Calculator
Work out how many wallpaper rolls you need the way a decorator does, by counting full-height strips (drops). Enter the room or wall size and your roll dimensions, and the calculator allows for the pattern repeat, deducts doors and windows, and can price the job. Metric or imperial.
Formula
Worked example
A 4 m x 4 m room has a 16 m perimeter and 2.4 m walls. With a 30 cm repeat, each strip is cut to ceil(2.4 / 0.30) x 0.30 = 2.4 m. After crediting one door, about (16 - 0.8) / 0.53 = 29 strips, plus 10% waste = 32 strips. A 10 m roll yields floor(10 / 2.4) = 4 strips, so 32 / 4 = 8 rolls.
Why the strip (drop) method beats a simple area sum
Hanging wallpaper is not like spreading paint over an area. You cut the paper into full-height vertical strips, called drops, and hang them side by side. The honest question is therefore how many strips the walls need and how many strips you can cut from one roll, not how many square metres are involved. This calculator counts strips: it divides the total wall width by the roll width to get the number of drops, then divides the roll length by the cut length of one drop to see how many drops each roll yields. Because a roll almost never divides evenly into whole drops, the leftover at the end of each roll is wasted, which is exactly why an area-only estimate quietly undercounts and leaves you a roll short. Working in strips captures that real-world waste.
How the pattern repeat changes everything
A pattern repeat is the vertical distance before the design starts again. To make the pattern line up across neighbouring strips, every drop has to be cut to a whole number of repeats, so the cut length is the wall height rounded up to the next repeat. A 2.4 m wall with a 30 cm repeat still cuts at 2.4 m, but a 2.4 m wall with a 64 cm repeat must be cut at 5 x 0.64 = 3.2 m, wasting 0.8 m off the top of every single strip. That is why a large repeat can add a roll or two even though the room has not changed. Set the repeat to zero for plain or free-match papers, where you simply trim top and bottom and lose almost nothing. The extra waste allowance on top covers trimming, the odd miscut and short offcuts that cannot reach floor to ceiling.
Doors, windows, units and cost
Switch between room mode, which finds the perimeter from a rectangular floor as 2 x (length + width), and perimeter mode, where you add the walls up yourself for an L-shaped or part-papered room. The calculator credits back roughly one strip width per door and per large window, since the strips over and under an ordinary opening are full of unusable offcuts; only deduct genuinely large openings and leave small windows in. Everything works in metric or imperial, and the roll width defaults to the European 53 cm or you can set the US 27 in. Turn on the cost estimate to multiply the rolls you buy by your price per roll in your chosen currency. The result is a buildable shopping figure: round up, buy one batch, and keep a spare roll for repairs.
Standard roll sizes and pattern-repeat waste
| Paper / region | Roll size | Typical repeat | Effect on cut length |
|---|---|---|---|
| European standard | 10 m x 53 cm | None / random | Cut at wall height, minimal loss |
| European, small repeat | 10 m x 53 cm | Up to 15 cm | Rounds up to next 15 cm |
| European, large repeat | 10 m x 53 cm | 50-65 cm | Can waste 0.5 m per strip |
| US double roll | ~11 yd x 27 in | Varies | Wider strips, fewer drops |
| Wall mural | Custom panels | Single image | Sized to wall, no repeat |
Common roll dimensions and a rule-of-thumb for the waste a repeat adds.
Frequently asked questions
Why does this ask for roll length and width instead of coverage?
Because wallpaper is hung in full-height strips, not spread by area. Knowing the roll length and width lets the calculator count how many strips fit across your walls and how many strips you can cut from one roll. That captures the waste left at the end of every roll, which a coverage-only estimate misses, so it is far less likely to leave you a roll short.
How do I handle the pattern repeat?
Enter the vertical repeat printed on the roll label, or 0 for a plain or random-match paper. The calculator rounds each strip up to a whole number of repeats so the design lines up between drops. A large repeat means more is trimmed off the top of every strip, which is why it can add a roll or two even when the room is unchanged.
Should I deduct doors and windows?
The tool credits roughly one strip width for each door and each large window, because the paper above and below an ordinary opening is mostly unusable offcuts. Only count genuinely large openings such as patio doors or a wall of glazing. Leave small or standard windows in, since trying to reuse the offcuts rarely works out.
How much spare should I buy?
The extra waste allowance (10% by default) covers trimming and miscuts. For a hard-to-match large repeat or a tricky room, add a few more percent or buy one extra roll. Always order every roll from the same batch or shade number, and keep leftovers for future repairs since dye lots sell out.