Question 1

How many rolls of wallpaper do I need?

Accepted Answer

Use the professional strip method, not simple area division. First count strips: divide each wall width by the roll width and round up. Then find the cut length per strip: wall height plus a 10 cm (4 in) trim allowance, rounded up to whole pattern repeats (plus half a repeat for half-drop match). Strips per roll = roll length divided by cut length, rounded down. Rolls = total strips divided by strips per roll, rounded up, plus 1 spare strip. The calculator above runs this exact math.

Question 2

What is pattern repeat and why does it make me buy more wallpaper?

Accepted Answer

Pattern repeat is the vertical distance between two identical points in the design, printed on the wallpaper label (for example 53 cm or 21 in). Every strip must be cut so the motif aligns with its neighbour at the seam, which means trimming off up to one full repeat per strip. The larger the repeat, the more paper is wasted per strip, so a big-repeat design can need 20-30% more rolls than a plain one for the same wall.

Question 3

Straight match vs half-drop: which needs more wallpaper?

Accepted Answer

Half-drop needs more. With a straight match every strip aligns at the same height, so the cut length is just the wall height rounded up to whole repeats. With a half-drop match (also called half drop or drop match) every other strip is offset by half the repeat, so each strip effectively needs an extra half repeat of length. Expect roughly 15-25% more rolls for a half-drop pattern compared to the same repeat on a straight match.

Question 4

How do I measure a wall for wallpaper?

Accepted Answer

Measure the width and height of every wall you plan to paper, in metres or feet, and enter each wall separately. Measure width along the baseboard and height from floor to ceiling. Add a 10 cm (4 in) trim allowance per strip for cutting at the ceiling and baseboard; the calculator adds this automatically.

Question 5

Should I subtract windows and doors when calculating wallpaper?

Accepted Answer

Subtract their area from the total square metres, but be careful with strip counts: you still need full-height strips on both sides of a window, plus short pieces above and below it, so a window rarely saves whole strips. Only openings that run nearly full height (at least 90% of the wall height, like sliding doors) save whole strips. The calculator deducts opening area and credits full-height openings automatically.

Question 6

How many strips (drops) do you get from one roll of wallpaper?

Accepted Answer

Divide the roll length by your cut length and round down. The cut length is wall height plus trim allowance, rounded up to whole pattern repeats. Example: a 10.05 m roll with a 2.65 m cut length gives 3 strips per roll (10.05 / 2.65 = 3.79, rounded down to 3) — that is 3 drops per roll. The leftover 2.10 m is too short for another full strip.

Question 7

Single roll vs double roll wallpaper: which is cheaper?

Accepted Answer

Not always the double roll. A double roll is simply twice the length of a single roll (same width), so it usually yields more than twice the strips because the end-of-roll leftover is shared. But if the double-roll price is more than double the single-roll price, singles can win on small walls. Compare total project cost, not price per roll; the cost comparison table in the calculator does this for your exact walls.

Question 8

Why must all wallpaper rolls come from the same dye lot?

Accepted Answer

Colours drift slightly between print runs, so two rolls from different batches can show a visible shade difference on the wall. Always order every roll you need, plus 1-2 spare strips, in one order from the same dye lot — the same batch number printed on the label. Reordering later risks a mismatched batch.

Question 9

How much extra wallpaper should I order?

Accepted Answer

Order 1-2 spare strips beyond the calculated total, not a flat percentage. The waste from pattern matching is already captured in the strip cut-length math, so adding a percentage on top double-counts waste and inflates the order. Spare strips cover installer mistakes, mis-cuts, and future repairs, and they must come from the same dye lot.

Question 10

What are the standard wallpaper roll sizes?

Accepted Answer

European/UK standard: 0.53 m wide x 10.05 m long (about 5.33 m2). US single roll: 20.5 in wide x 16.5 ft long (about 28 sq ft). US double roll: 20.5 in wide x 33 ft long (about 56 sq ft). Wide-width: 1.06 m x 15.6 m. Peel-and-stick is often sold as panels rather than rolls, so check the panel size on the listing.

Question 11

Can I use this calculator for ceilings or stairwells?

Accepted Answer

For stairwells, measure the longest drop from the highest ceiling point to the lowest stair and use that as the wall height; the calculator's rectangular-wall model then gives a safe estimate. For ceilings, strips run across the room width instead of up the wall. Sloped ceilings and curved walls fall outside the rectangular model, so treat the result as a starting estimate and confirm with your installer.

Question 12

What does random match or no repeat mean on wallpaper?

Accepted Answer

Random match (no repeat, repeat = 0) means the design has no motif to align: stripes, textures, and grasscloth. Strips can be cut starting anywhere on the roll, so there is no pattern-matching waste and the cut length is simply wall height plus trim allowance. This is the most economical option for roll count.

Question 13

How much does it cost to wallpaper a room?

Accepted Answer

Multiply the number of rolls by the price per roll, then add installation if you hire a pro: typically $2-$4 per square foot ($22-$43 per m2), or $40-$80 per single roll depending on pattern complexity and wall prep. As a rough comparison for the wallpaper or paint decision: wallpaper material often costs more per square metre than paint, but a single feature wall can be cheaper than repainting a whole room.

Wallpaper Calculator

◆ Your walls & wallpaper

◆ Breakdown

Roll-by-roll plan

Wall diagram

◆ Single vs double roll

◆ Why pattern repeat eats wallpaper

Straight match

Half-drop match

◆ Worked examples

Example 1 — Feature wall, straight match (metric)

Example 2 — Two walls + sliding door, half-drop (metric)

Example 3 — Plain wallpaper, no repeat (imperial)

◆ Methodology

◆ Frequently asked questions

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