Why does the pattern repeat matter so much?

Each drop has to start at the right point in the pattern, so up to a full repeat is cut off and discarded at the top of every strip. A 64cm repeat on a 2.4m wall wastes far more than a random match.

Construction & Homefinishing

Wallpaper Calculator

Wallpaper rolls from wall area. A standard roll covers about five square metres in practice rather than the ten it measures, because pattern matching wastes a great deal.

Also called: wallpaper rolls needed, wallpaper quantity.

Rolls

4.23

4.23 rolls for 20 m² over 1 coat(s), including 10% wastage.

Area after deductions (m²)

Area across all coats (m²)

Before wastage

3.85

Area one unit covers (m²)

5.2

How this is calculated

Method and background

How this is calculated

Area divided by the usable coverage of a roll, plus wastage. The usable figure is the one to be careful about: a standard European roll is 10 metres by 0.53, so 5.3 square metres nominal, but a patterned paper with a large repeat can lose a fifth of that to matching. A plain or random-match paper wastes almost nothing.

quantity = area * coats / coverage per unit, plus wastage

A: Net area (m2)
c: Coats (count)
r: Coverage per unit (m2)
s: Wastage (decimal)

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

a room in patterned paper

Length (m): 14
Width or height (m): 2.7
Or enter the area directly (m²): 0
Openings to deduct (m²): 3
Area one roll covers (m²): 5.2
Coats or layers: 1
Wastage: 10%

Rolls7.36

34.8 / 5.2, worked by hand

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a plain paper wastes less

Length (m): 14
Width or height (m): 2.7
Or enter the area directly (m²): 0
Openings to deduct (m²): 3
Area one roll covers (m²): 5.2
Coats or layers: 1
Wastage: 0%

Rolls6.69

boundary

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Method and limits

What it assumes

Coverage entered is usable coverage after pattern matching.

What it deliberately does not model

A large pattern repeat can push effective waste past twenty percent and is not derived here.
Rolls should come from one batch, as shade varies between runs.

Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator

Frequently asked questions

Why does the pattern repeat matter so much?: Each drop has to start at the right point in the pattern, so up to a full repeat is cut off and discarded at the top of every strip. A 64cm repeat on a 2.4m wall wastes far more than a random match.