Wallpaper Rolls for Room Calculator
Wallpaper is unforgiving when you run short: a late top-up from a different dye lot rarely matches, so getting the roll count right the first time matters. This calculator estimates how many rolls a room needs. Enter the room length and width, the wall height, the total area of doors and windows to leave uncovered, and the usable coverage of one roll, and the tool computes the wall area, subtracts the openings, and divides by the usable coverage per roll to give the number of rolls, rounded up to whole rolls. The wall area is the room perimeter (twice the length plus twice the width) times the height. The usable coverage matters more than the printed roll size, because trimming, pattern matching and the short end of each drop all create waste, so a roll covers less wall than its nominal area suggests. The coverage figure is editable so you can lower it for a large pattern repeat, which wastes more. The result is rounded up, and buying one spare roll from the same batch is strongly advised so future repairs match. Every figure is computed deterministically from the formula shown below, with a worked example that reconciles exactly to the calculator's defaults so you can follow each step.
Rolls needed is the wall area minus openings, divided by usable coverage per roll: (perimeter x height - openings) / roll coverage. A 12 x 14 room with 9 ft walls and 60 sq ft of openings has 408 sq ft to cover, needing 14.57 rolls (round up to 15) at 28 sq ft per roll.
Wallpaper rolls formula
Wall area = ( 2 x ( length + width ) ) x height
Area to cover = wall area - openings
Rolls = area to cover / usable coverage per roll
Rolls to buy = round rolls up to the next whole number
Multiply the perimeter by the height, subtract the openings, then divide by the usable coverage of a roll. Round up, and buy one spare from the same batch.
Worked example
Suppose a room is 12 by 14 feet with 9-foot walls, 60 square feet of openings, and each roll usefully covers 28 square feet.
- Perimeter = 2 x (12 + 14) = 52 ft
- Wall area = 52 x 9 = 468 sq ft
- Area to cover = 468 - 60 = 408 sq ft
- Rolls = 408 / 28 = 14.57
- Rolls to buy = round 14.57 up to 15
You need 14.57 rolls, so buy 15 (plus a spare). These are the calculator's default inputs, so the result above matches the widget exactly.
Rolls by area to cover
Rolls needed at 28 square feet usable coverage per roll.
| Area to cover | Rolls (exact) |
|---|---|
| 200 sq ft | 7.14 |
| 408 sq ft | 14.57 |
| 560 sq ft | 20.00 |
| 700 sq ft | 25.00 |
Usable coverage is lower than the printed roll area because of trimming and pattern match.
Wallpaper rolls calculator: frequently asked questions
How many rolls of wallpaper does a room need?
Find the wall area by multiplying the room perimeter by the wall height, subtract the area of doors and windows, then divide the result by the usable coverage of one roll. Round up to whole rolls, and add one extra for pattern matching and waste. The usable coverage per roll is less than the full roll area because of trimming and pattern repeats.
What is usable coverage per roll?
A standard wallpaper roll states a total area, but you cannot use all of it: trimming, pattern matching and the last short strip of each drop create waste. The usable coverage, often around 25 to 30 square feet for a standard double roll after waste, is what actually goes on the wall. This calculator uses the usable figure you enter, which you can adjust for your roll and pattern.
Does the pattern repeat affect how many rolls I need?
Yes. A large pattern repeat means each strip must be cut to line up with its neighbor, wasting more at the top or bottom of each drop. The bigger the repeat, the lower the usable coverage per roll and the more rolls you need. Reduce the usable coverage you enter for large-repeat patterns, and always buy a spare roll.
Should I buy extra rolls?
Yes. Buy at least one extra roll beyond the calculated number, ideally from the same batch, so the color and pattern match exactly. Dye lots vary between batches, and a later top-up may not match. The spare also covers mistakes and future repairs. Rounding up plus one spare is a safe rule.
Do I subtract doors and windows?
Subtracting large openings like doors and picture windows gives a tighter estimate and avoids buying too much. For small windows, many people skip the deduction to leave a margin for waste. Enter the total opening area you want to deduct; the calculator subtracts it from the wall area before dividing by roll coverage.
Official sources
- Area and length measurement reference: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.