Wallpaper Calculator
Work out how many rolls of wallpaper a room needs, with a pattern-repeat allowance and cost.
How to use this calculator
- 1Measure the area. For an irregular space, split it into rectangles, work each out, and add them.
- 2Set the unit you measured in — the calculator converts everything for you.
- 3Check the coverage figure against the bag or tin you are actually buying; it varies between brands.
- 4Leave the waste allowance on. Running short mid-job costs far more than one spare unit.
How the calculation works
Units = ⌈ (Area × (1 + waste)) / Coverage per unit ⌉- Area
- Surface area of the job
- waste
- Allowance for cuts, breakage and spillage
- ⌈ ⌉
- Round up — you cannot buy a fraction of a unit
Every dimension is converted to metres internally, so feet, yards and metres can be mixed with inches or centimetres without error.
Usable coverage is always less than the roll area printed on the label, because each drop is cut to wall height and the remainder is usually too short to reuse. A 5.3 m² roll typically yields closer to 5 m² of hung paper.
Pattern repeat is the dominant cost driver. A straight match wastes least; a drop match, or a repeat over 50 cm, can push waste beyond 25% since every drop must begin at the same point in the design.
Worked example
A 20 × 12 ft area
- 1.20 ft × 12 ft = 240 sq ft, which is 22.30 m².
- 2.Divided by the coverage per roll, that gives the raw requirement.
- 3.A 15% waste allowance is added, then the figure is rounded up to whole rolls.
Result: See the result panel — it updates live as you change the numbers.
What this assumes, and where it stops
Assumptions
- The area is flat and regular as described. Slopes, steps and obstructions change the quantity.
- Coverage figures are the manufacturer’s stated values, which assume good conditions and an even surface.
- The area entered is the wall area to be papered — perimeter multiplied by height.
Limitations
- This estimates material only — not labour, tools, delivery, hire or disposal.
- Manufacturer coverage varies between brands and batches. Always check the packaging.
- Does not subtract doors and windows. On a normal room that is a useful safety margin; on a wall that is mostly glazing, measure the papered area directly.
- Paste, lining paper and trim are not included.
Common questions
How many rolls do I need for an average room?
For a 4 × 4 m room with 2.4 m ceilings the walls come to about 38 m². At roughly 5 m² of usable coverage per roll that is 8 rolls before waste, so 9 or 10 with a pattern allowance. Buy a spare and check every roll shares the same batch number.
Why does pattern repeat waste so much paper?
Because every drop has to start at the same point in the design so the pattern lines up across the wall. With a 64 cm repeat you may discard up to 63 cm from the top of each drop. A drop match, where alternate strips are offset, wastes more still.
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
Related calculators
Tools people commonly use alongside the wallpaper calculator.