Wallpaper Calculator: How Many Rolls?

Measure each wall separately

Measure the width of each wall to be covered and the hanging height in metres. The optional second and third widths are for walls of the same height. Wallpaper is hung in vertical drops, so round each wall’s required drop count up before summing. Combining wall widths and rounding only once can underestimate the count at corners.

The calculator does not automatically subtract doors and windows. A full drop may still be needed to preserve a continuous pattern around an opening. If a large opening seems to save material, make a cutting plan with the installer and check which offcuts really fit. Net wall area alone cannot establish a full-drop count.

Count drops and effective cut length

For each wall, required drops equal its width divided by roll width, rounded up. Base cut length equals wall height plus the combined top and bottom trimming allowance. When the label gives a vertical repeat, round this cut length up to a full repeat. Divide roll length by effective cut length and round down to full drops per roll. Finally divide total required drops by that yield and round up to whole rolls. If one full drop cannot fit, the calculator reports an error.

For one wall 4 m wide and 2.5 m high, take a 0.53 m wide, 10 m long roll with a 0.53 m repeat and 0.10 m combined trim. Width needs ceil(4 ÷ 0.53) = eight drops. Base cut is 2.60 m; round to five repeats, or 2.65 m. One roll yields floor(10 ÷ 2.65) = three full drops. Eight drops need ceil(8 ÷ 3) = three whole rolls. The third roll leaves one theoretical full drop after the wall is covered.

Check pattern and product before ordering

Check whether the pattern is free match, straight match or offset match. Vertical repeat alone does not model a half-drop offset, alternating A/B rolls, reverse hanging or the use of short offcuts. If the label names any of these, take the estimate to the supplier or installer for a cutting plan rather than assuming the same yield per roll.

Check the exact product code, roll dimensions and batch number. Buying the same batch together helps avoid visible colour variation. Any price you enter is your own per-roll figure, not a live shop quote. The subtotal excludes paste, surface preparation, labour, delivery and an optional spare roll for later repairs. Ask for the seller’s return policy before adding a contingency roll.

Why square metres alone can mislead

Two rolls with similar square-metre coverage may yield different numbers of usable drops because their lengths and pattern repeats differ. A small increase in hanging height can reduce a roll from three full drops to two, sharply increasing the order. If the floor or ceiling is uneven, measure height in several places and plan around the longest full drop needed. Record both dimensions and the label’s pattern symbols when asking a supplier to confirm the order.