What this calculator does

Wallpaper estimates need wall area, roll coverage and a waste allowance for trimming, mistakes and pattern matching.

Formula used

Net wall area equals wall width multiplied by height, minus openings. The waste allowance is added, then the adjusted area is divided by roll coverage.

How to read the result

Pattern repeat, batch matching and awkward corners can increase the number of rolls. Buying a little extra from the same batch is often safer than reordering later.

Assumptions

  • Uses square metre coverage.
  • Subtracts doors and windows only when their area is entered.
  • Does not model pattern repeat drop matching in detail.

Sources and checks

This calculator uses a standard public formula. Where rules or thresholds can change, source links are listed on the relevant page.

Frequently asked questions

Should I subtract windows and doors?

Subtract large openings if you know their area, but keep a waste allowance because offcuts and pattern matching still use material.