Wallpaper Calculator
How many rolls of wallpaper a room needs from wall size, roll coverage, doors, windows and waste.
How it works
wall area = length × height − 21 sq ft per door − 15 sq ft per window · rolls = ⌈area × (1 + waste%) ÷ roll coverage⌉
The total wall length times the height gives gross wall area; a standard door removes about 21 sq ft and a typical window about 15, so those are subtracted. A waste allowance is added for trimming and matching the pattern, then divided by the coverage of one roll and rounded up, since rolls are sold whole. Rolls vary — a “double roll” covers far more than a single — so enter the coverage printed on the roll you’re buying.
Worked example
A room with 40 linear feet of wall at 8 ft high is 320 sq ft. Take out one door (21) and two windows (30) for 269 sq ft to cover; add 15% waste (309 sq ft) and divide by 56 sq ft per roll to get 5.5 — so buy 6 rolls.
Frequently asked questions
How much does one roll cover?
A standard US single roll covers roughly 56 sq ft after trimming, but wallpaper is often sold in double or triple rolls that cover proportionally more. Always use the coverage figure on the packaging — that’s the number this calculator needs.
Why is the waste allowance higher than for paint?
Wallpaper has to be trimmed at top and bottom and, for patterned papers, matched at every seam — the bigger the pattern repeat, the more you cut off and discard. 15% suits most papers; go to 20–25% for large-repeat patterns.
Should I buy an extra roll?
It’s wise. Keeping one spare from the same batch means you can repair a damaged strip years later without a visible color mismatch — later print runs rarely match exactly, and a single roll is cheap insurance.
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This calculator is for educational purposes. Double-check important results before acting on them.