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Wallpaper Calculator

Updated How we build and test

Enter the room size, doors and windows, and the coverage printed on the wallpaper label. The calculator subtracts the openings, allows extra for matching the pattern and trimming at the ceiling and floor, and tells you how many rolls to buy.

For one accent wall, enter its width here and 0 for the width.

21 sq ft each.

15 sq ft each.

sq ft

Use the coverage on the label. Rolls are sold in different sizes.

%

More for a large pattern repeat.

$

Rolls to buy

Enter the room size to see how many rolls of wallpaper to buy.

How to use the wallpaper calculator

  1. Measure each wall you will paper and the height from the baseboard to the ceiling.
  2. For a single accent wall, enter its width as the length and 0 as the width.
  3. Check the label for the coverage per roll. Rolls come in different widths and lengths, and many US papers are sold priced per single roll but packaged as double rolls, so use the coverage stated for the roll you are buying.
  4. Set the matching allowance: 10–15% for a small or random pattern, more for a large drop match.

Wallpaper formula

Wall area = perimeter × height − doors × 21 − windows × 15
Usable coverage per roll = coverage × (1 − allowance %)
Rolls = wall area ÷ usable coverage, rounded up

Worked example: a 14 × 12 ft room

  1. Wall area: 2 × (14 + 12) × 8 − 21 − 30 = 365 sq ft.
  2. Usable coverage of a 56 sq ft roll with 15% allowance: 56 × 0.85 = 47.6 sq ft.
  3. Rolls: 365 ÷ 47.6 = 7.67, so buy 8 rolls.

Why the pattern repeat matters

Each new strip has to line up with the pattern on the one before it, so you cut part of every roll away. A paper with a large repeat or a drop match wastes more than a plain or random-match paper. If the label gives a repeat of 20 in or more, raise the allowance to 20–25%.

Tips

  • Buy all rolls from the same batch (run) number; colors can differ between runs.
  • Keep one spare roll for repairs.
  • Paper the wall above doors and windows too; the deductions here already allow for the small strips.

Questions

How many rolls for an accent wall?

Measure the wall, enter its width as the length and 0 for the width. A 12 ft wide, 8 ft high wall with no openings needs about 96 sq ft, or 3 rolls of 56 sq ft with 15% allowance (96 ÷ 47.6 = 2.02).

Should I subtract windows?

Yes, but the paper above and below them is still used, so only the opening itself is deducted.

What does the coverage on the label mean?

It is the area one roll covers before waste. The allowance in the calculator takes off what you lose to matching and trimming.

Sources

  1. NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
    Used for: Exact foot and inch definitions.

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