Wallpaper calculator

Measure your walls and identify the exact roll

Enter each wall width and height as a separate row, even if several walls happen to match. The calculator divides each wall into full-height wallpaper drops based on the roll's usable width. Use the dimensions printed by the wallpaper manufacturer: roll widths, roll lengths and repeats vary, especially between specialist murals, European rolls and North American products.

Enter a trimming allowance for the extra length required at the top and bottom of every drop. Add the stated pattern repeat and any separate matching allowance when appropriate. The calculator reports opening area for reference, but does not automatically remove windows and doors from the full-height drop count. That conservative approach avoids assuming every small piece can come from a saved offcut.

Why wall width and height matter separately

Measure horizontally across the wall from one finished boundary to the next. Measure vertical height in several places because older rooms can have uneven floors and ceilings. Use the greatest relevant height for an unbroken drop and account for trimming. A wall that is 4 m wide and another that is 3 m wide may need different numbers of drops even if both are the same height.

Keep alcoves, chimney breasts and narrow returns as separate walls. A window over a radiator does not automatically eliminate the need to paper full-height sections around it, and a door may need short pieces above. Use a separate paper plan when cuts can genuinely be shared. The estimator's full-height approach favours predictability over optimistic material reuse.

The drops-per-roll method

Full-height drops on each wall equal wall width divided by roll width, rounded upwards. Base drop length equals measured wall height plus trimming and matching allowances. If the wallpaper has a straight pattern repeat, round that prepared length upwards to a whole multiple of the repeat. If repeat is zero, use the prepared length directly.

Usable drops per roll are the manufacturer's roll length divided by that prepared drop length, rounded down. Rolls for a wall equal its drops divided by usable drops per roll, rounded up. This estimator calculates roll groups wall by wall, then sums them. That avoids promising that leftovers from a shorter wall can always serve a taller one.

Worked example: plain and patterned wallpaper

Consider one wall 4 m wide and another 3 m wide, both 2.4 m high. A roll 53 cm wide and 10.05 m long gives eight drops for the wider wall and six for the narrower wall. Add 100 mm trimming per drop, so each plain drop is 2.5 m long. A 10.05 m roll supplies four complete plain drops.

For plain wallpaper, the eight-drop wall takes two rolls and the six-drop wall takes two more, for four rolls using this wall-by-wall estimator. With a 640 mm straight repeat, each 2.5 m drop becomes 2.56 m. Only three such drops fit per roll, so the walls require three and two rolls respectively: five rolls before an extra allowance.

Pattern matching can change the count materially

A straight pattern repeat means the print repeats after a stated length, not that every pattern is matched by cutting exactly that number of millimetres. The calculator rounds prepared drops to repeat multiples as an estimator. Confirm whether the chosen product has a straight match, free match, half-drop match or another layout described on its label.

Half-drop and complex matches can require alternating strip alignment and additional waste, which this simplified formula does not model precisely. Expensive textured, hand-printed or mural systems may have panel numbering or special fitting instructions instead of ordinary repeat dimensions. Follow that product's own pattern plan rather than treating a generic roll estimate as sufficient.

What to do with doors, windows and short spaces

Enter opening dimensions if you want a reference area for the wall, but the output explicitly does not deduct those square metres from the number of drops. Some rolls may provide small pieces above doors or under windows, yet available remnants depend on the pattern, cutting position and installer's sequence. Automatically subtracting opening area could undercount rolls.

Where a wall is mostly glazing or the layout contains repeated short panels, make a detailed strip-by-strip diagram. Measure each piece, include repeat alignment and test how it fits the purchased roll length. That can be more economical than a full-height estimate, but it is a different task from this straightforward conservative calculator.

Waste, batch numbers and purchasing decisions

Once the base rolls are known, an optional percentage allowance adds extra whole rolls and rounds upwards again. Consider damage, miscuts, errors in room height, matching complexity and whether you want a spare roll for later repairs. The preset is not a universal recommendation, and a complex wall may need a more detailed take-off.

Wallpaper production batches can differ slightly in colour. Check the supplier's batch or dye lot when ordering, especially if you expect to use a spare later. Enter a genuine price per roll only if it applies to the selected design and quantity. The website does not quote stock availability or retailer prices.

Avoid the most common roll-count errors

Do not assume total wall area divided by roll area gives the right number of rolls. That ignores the fact that a remaining length shorter than one complete drop can be unusable for the main wall. Do not confuse a 64 cm pattern repeat with a 64 mm repeat or treat the roll width as the repeat dimension.

Check height after flooring changes, skirting alterations or ceilings being lined. Confirm whether the wallpaper includes a separate trimming margin and make sure you have not added it twice. The final check should be a realistic fitting sequence, with the correct wallpaper batch and the manufacturer's installation instructions available on site.

Common questions

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