Pattern Repeats Explained: How Many Rolls of Wallpaper to Buy

Buying wallpaper is the one decorating job where counting square metres gets you the wrong answer. Paper comes in strips, and each strip must start at the right point in the pattern, so the amount you waste depends on the size of the pattern as much as the size of the wall. Two rooms with identical dimensions can need seven rolls of a plain paper and nine of a big floral. This guide explains what the pattern repeat is, the three ways patterns match, and how to calculate rolls strip by strip, with worked examples you can follow with a tape measure.

Roll sizes and what the label tells you

Standard UK wallpaper rolls are usually around 10.05 metres long and about 52 to 53 centimetres wide. That 10.05 m by 0.53 m size is the long-established norm, but it is not universal: some designer and non-woven papers, wide-width rolls and murals use different dimensions, and imported rolls vary. Always take the size from the label or product page of the paper you intend to buy, and not from a general rule.

The label also gives three things you need for the calculation:

• Pattern repeat. The vertical distance, in centimetres, before the design repeats. It may be zero for plain or textured papers.
• Match type. Free match, straight match or drop (offset) match.
• Batch number. Rolls with the same batch number have the same colour. Rolls from different batches can show shade differences that are obvious next to each other. Buy all your rolls together, and check the numbers match.

Labels also show how to hang the paper (paste the wall or paste the paper), whether it is washable and how to remove it, and whether the paper must be hung strip by strip, in alternating directions, or all the same way up.

The three kinds of match

Free match

A free match pattern, such as a plain, textured or random all-over design, can be hung without lining up the pattern across strips. There is no repeat to match, so waste is minimal: you only need to allow a little extra length for trimming at the top and bottom of each drop.

Straight match

In a straight match, the pattern lines up across the join at the same height on every strip. The pattern repeat then dictates the minimum length of paper per drop, because each strip must start at the same point in the design. Every strip is cut to a multiple of the repeat, rounded up from the wall height plus trimming allowance.

Drop (offset) match

In a drop match, sometimes called a half-drop, the pattern lines up diagonally: the strip next to the first starts half a repeat lower (the usual form), so the pattern steps down across the wall. This wastes more paper, since alternate strips begin at different points in the design, so the cutting length effectively includes half a repeat extra. Large drop-match repeats waste the most paper of all.

Working it out step by step

1. Measure the wall width. Add up the length of each wall you will paper, ignoring doors and windows at first. For a whole room, use the perimeter.
2. Measure the height. Measure from the skirting (or the picture rail, if you are papering below it) up to the ceiling or cornice. Measure in a couple of places, since walls and ceilings are rarely level.
3. Add a trimming allowance. A margin of about 5 centimetres at the top and 5 at the bottom (10 centimetres total) is commonly used so you can trim the edges cleanly. Add this to the wall height to get the drop length.
4. Allow for the pattern. If there is a repeat, round the drop length up to the next multiple of the repeat. For a drop match, round up to the repeat, then add half a repeat.
5. Count the strips. Divide the total wall width by the roll width (0.53 m) and round up. Corners and the edges of windows and doors often reduce the usable width of a strip, so some rounding up is normal.
6. Strips per roll. Divide the roll length by the drop length and round down. You cannot join short offcuts without a visible seam in a patterned paper, so ignore any leftover shorter than a drop.
7. Rolls required. Divide the number of strips by the strips per roll and round up.

The wallpaper roll estimator performs these steps with your repeat and match type.

Worked examples

Illustrative numbers. A room with a perimeter of 14 m and a wall height of 2.4 m, using a standard roll of 10.05 m x 0.53 m. We will ignore doors and windows to keep the arithmetic clear.

• Strips: 14 / 0.53 = 26.4, rounded up to 27 strips.
• Drop length with trim: 2.4 + 0.1 = 2.5 m.

The same room needs seven rolls of plain paper but nine of a patterned one. Notice how sensitive the result is: in the straight match example, the strips per roll falls from four to three because the drop length rises from 2.50 m to 2.56 m, so four drops would need 10.24 m, about 19 cm more than the roll holds. Always check the arithmetic at the limit, and consider buying one extra roll rather than risking a shortfall. If the wall height is 2.3 m instead, the plain paper still yields four strips per roll, but the patterned papers might change too. A small change in height can alter the roll count by a whole roll.

Subtracting doors and windows can lower the number of strips, but with patterned papers the saving is less than you might expect, because the strips above doors and below windows need to be cut from full drops. A common rule is to deduct a strip for an average door or a large window, but not for small windows. Never deduct more than you can justify, and err on the generous side.

Buying extra, and keeping spare

Order at least one spare roll beyond your calculation for mistakes, and keep any spare for future repairs. The batch number is important. Wallpaper discontinues quickly and colours vary between print runs, so a spare roll from the original batch is the only way to patch a damaged area invisibly years later. Do not open all rolls before you check them, and if you spot a fault such as a colour defect or a printing flaw, stop and contact the supplier before hanging. Most suppliers will not accept returns of paper that has been cut or hung.

Preparing the wall

• Strip old paper completely if it is not firmly stuck, and wash off old paste residue.
• Repair the surface. Fill holes and cracks, sand smooth, and dust. Wallpaper will show bumps and ridges, especially thin papers under side light.
• Seal the wall. New plaster, bare plasterboard and porous surfaces should be primed or sized as the paper manufacturer recommends, so the paste does not soak in too fast. If you are papering over new plaster, our guide to painting new plaster covers the drying and sealing issues, which apply here too.
• Lining paper can smooth a rough wall and give a better base for expensive papers. Hang it horizontally, so its seams do not coincide with those of the topper.
• Check for damp. Wallpaper over damp walls will bubble and mould. Fix the cause first.
• Old paint or paper in houses before 2000 can occasionally conceal materials you should not disturb; if you suspect asbestos in textured coatings, do not scrape them.

Hanging: starting point and technique

1. Find a starting point. A strip is generally hung first at the focal point, such as the centre of a chimney breast, or from the corner furthest from the main window. Avoid starting in a corner, since walls and corners are almost never plumb.
2. Mark a plumb line with a spirit level or plumb bob, and hang the first strip against it, not against the corner.
3. Cut the strips with the allowance at top and bottom, and number them on the back in pencil so they go up in order.
4. Paste and book. Paste the paper (or the wall, for paste-the-wall papers), fold the pasted sides together without creasing and leave it for the soaking time on the label, which allows the paper to expand before it goes on the wall.
5. Smooth and trim. Brush from the centre outwards to push out air, trim top and bottom with a sharp knife against a straight edge or a wallpaper scraper, and wipe excess paste from the surface at once.
6. Butt the joins. Do not overlap. Roll the seams lightly, unless the paper is embossed or flocked, when a roller would flatten the texture.

Switch off the power before working around sockets and switches, and loosen the faceplate rather than papering over it. Cut a small cross in the paper over the socket, trim neatly, and let the paper dry before switching power back on.

Common mistakes

• Calculating by square metres. It almost always underestimates for patterned paper.
• Forgetting the trim allowance, then finding the strip is short at the ceiling.
• Mixing batch numbers, giving a colour change across the wall.
• Starting in a corner and ending with a crooked first strip.
• Pasting too wet. Thin papers can stretch and tear, and overly wet walls take longer to dry.

Where to go for help

For persistent damp, cracking walls or doubts about what is under old layers of paper, ask a decorator, surveyor or builder. This guide is general information; the paper manufacturer's instructions take priority for the product you buy.

Sources

• Planning Portal: Decorations
• GOV.UK: Approved Documents