How Much Wallpaper Do I Need? A Complete Guide

How to measure, how to allow for pattern repeat, and why the same room can need seven rolls or nine.

Almost every wallpaper ordering mistake comes down to one thing: people calculate the area of their walls, divide by the area of a roll, and order that many. It is a reasonable instinct and it is wrong, because wallpaper hangs in full-height drops and the offcut at the bottom of each drop cannot be used anywhere else. Pattern repeat then makes the gap between the area calculation and the real figure much wider still.

This guide walks through the correct method, with a worked example showing how a single design choice changes the order by two rolls.

01Know how your wallpaper is sold

Roll dimensions are not standardised worldwide, and some wallpapers are not sold by the roll at all. Assuming the wrong format is a quick way to order short.

Always check the specification for the individual reference rather than assuming. Two designs from the same brand can be sold on different bases, and width in particular varies far more than people expect.

One point on American rolls that catches people out regularly. A double roll is a single continuous length equivalent to two singles, not two separate rolls. The advantage is that a longer continuous length yields more usable drops with less waste, which is exactly why they are sold that way.

02The measurements you need

Three numbers, and one of them needs more care than people give it.

1. Wall height, floor to ceiling. Measure in at least three places along the run. Floors settle and ceilings are rarely level, and a room can easily vary by 3cm end to end. Use the largest measurement, not the average.
2. Total width of the walls to be covered. For a full room this is the perimeter. For a feature wall it is just that wall.
3. Pattern repeat, taken from the product specification rather than measured off a sample, along with the match type.

Add a trim allowance of about 10cm to the wall height. This gives you the margin to align the pattern and cut cleanly at the ceiling and skirting. Cutting it finer than that is how a drop ends up 2cm short at the bottom.

03The calculation, step by step

The first two steps are the same whatever the paper. The last step depends on how it is sold.

1. Cut length. Wall height plus 10cm trim allowance. Adjust for pattern repeat as set out in the next section.
2. Drops needed. Total wall width divided by the width of the paper. Always round up.
3. If sold by the roll: work out drops per roll by dividing roll length by cut length, rounding down, then divide drops needed by that figure and round up to whole rolls.
4. If sold by the metre: multiply drops needed by cut length, then round up to the supplier's ordering increment.

For roll-sold papers, the two rounding directions pull against each other, and that is the whole reason area-based calculations underestimate. Rounding down on drops per roll is where the waste lives.

04Pattern repeat, the part that catches everyone

The repeat is the vertical distance before the design starts again. How much it costs you depends on the match type, which will be stated on the product specification.

Free match, also called random match

Textures, plains, grasscloths and some stripes. Nothing needs aligning between drops, so no extra allowance is needed. Some can even be hung with alternate drops reversed to even out shading.

Straight match

The pattern aligns horizontally across every drop at the same height. Each drop must be cut at a whole number of repeats, rounded up to cover the required length.

So if you need 2.5m and the repeat is 52cm, five repeats gives 2.6m and four gives 2.08m. You cut at 2.6m. The 10cm difference is waste on every single drop.

Half drop, also called offset match

Alternate drops are shifted down by half a repeat, which is what produces the diagonal rhythm across the wall. Calculate the cut length as for a straight match, then allow more, because the offset produces additional waste at the start of alternate drops. Adding one extra roll over the straight match figure is the usual working allowance.

A large repeat is a design decision with a budget attached. On a tall room, a 64cm repeat can add a third to the order.

05A worked example, sold by the roll

A room 4m by 3m, with a ceiling height of 2.4m. Standard European rolls, 10.05m long and 0.53m wide.

Identical room, identical measurements, two extra rolls. That difference is invisible if you calculate by area, and on a hand-printed paper at £200 a roll it is a £400 surprise.

06Wallpaper sold by the metre

Many of the European houses, and most wide-width and contract wallcoverings, are sold by the linear metre rather than by the roll. The paper is cut to length from a continuous roll, which changes the arithmetic in your favour.

The saving is real. With roll-sold paper you buy whole rolls, so a room needing 6.75 rolls costs you seven. With metre-sold paper you buy the length you actually need, so the waste that comes from rounding up disappears. On an expensive reference that difference is worth having.

How to calculate it

1. Work out your cut length exactly as before, wall height plus 10cm trim, rounded up to a whole number of repeats if the paper is a straight or half drop match.
2. Divide the total wall width by the width of the paper and round up. That is your number of drops.
3. Multiply drops by cut length. That is your linear metre requirement.
4. Round up to the supplier's ordering increment, and add your extra allowance on top.

Notice the wider paper has also cut the number of drops from 27 to 16, which means eleven fewer seams on the wall. That is a large part of why wider formats are specified on better projects, quite apart from the ordering economics.

What to watch

• Minimum order quantities. Many metre-sold references carry a minimum, and some are sold only in set multiples. Check before you build a budget around an exact figure.
• Cut to order means non-returnable. Once a length is cut from the roll it usually cannot be returned. Order samples and confirm your measurements first.
• Width varies by reference. Do not assume a brand's standard width applies across its whole range.
• You still need a single batch. Buying by the metre does not change this. Order the full quantity in one go.
• Round up, always. If your calculation gives 40.96m, order 41m at an absolute minimum. Suppliers cut to the metre and will not add a few centimetres of goodwill.

07Doors, windows and awkward rooms

The instinct is to subtract doors and windows from the perimeter. Resist it in a normal room. The offcuts from above a door and above and below a window are rarely usable elsewhere, and the drops either side of an opening still have to be cut to full height. Measuring the full perimeter and treating those offcuts as your working allowance is both simpler and more reliable.

Deduct only where an opening is genuinely large, such as full-height glazing or wide bifold doors, and even then deduct conservatively.

Rooms that need more, not less:

• Stairwells. Notoriously wasteful because of the raking cuts. Add 15 per cent as a minimum, and get a decorator to measure if the drop is a long one.
• Sloping ceilings and dormers. Every angled cut wastes most of a drop.
• Chimney breasts and alcoves. Each return is effectively another corner, and corners cannot be papered around in one piece.
• Rooms with many corners. Drops are cut at every internal corner rather than wrapped, so a broken-up room uses more than its perimeter suggests.

08Batch numbers, and why you order extra

Wallpaper is printed in batches, and colour varies between them. Two rolls of the same reference from different batches can be visibly different on the wall, particularly in pale grounds and hand-printed papers. Every roll for a room should come from a single batch, and the batch number is printed on the label.

This is the reason to order generously the first time. Going back for one more roll three weeks later frequently means a different batch, and no supplier can promise otherwise.

• Add at least one extra roll on any full room.
• Add two on large repeats, hand-printed papers, or anything discontinued or imported on long lead times.
• Keep a full offcut after hanging. Repairs to a damaged patch are straightforward with matching paper and impossible without it.

09Grasscloth and murals

Grasscloth and natural fibres are hung as a free match, so no repeat allowance is needed, but colour variation between and within rolls is inherent to the material rather than a fault. Order everything together, and expect the panels to read as panels. That is the character of the product.

Panoramic panels and murals are made to your wall dimensions and are not calculated by the roll. Measure the wall accurately, in several places, and send the dimensions with the order. These are usually made to order and non-returnable, so a site check before ordering is worth the delay.

10The mistakes we see most often

• Calculating by area rather than by drops. Always underestimates.
• Measuring the ceiling height once, in the corner where it happens to be lowest.
• Missing the pattern repeat entirely, or reading the repeat and ignoring the match type.
• Rounding drops per roll up instead of down. A roll cannot yield a partial drop.
• Subtracting every door and window, then ordering short.
• Ordering exactly the calculated figure with no margin at all.
• Assuming an American double roll is two rolls.
• Discarding all the offcuts, leaving nothing for repairs.

Frequently asked questions