Wallpaper Roll Estimator
Enter your wall dimensions and roll size — the estimator subtracts doors and windows and adds waste for pattern matching.
Runs entirely in your browser — your numbers never leave this page.
How it works
Wallpaper math is area math plus a pattern tax: every strip must start at the same point in the pattern, so matching a large repeat wastes paper. The estimator works in three steps:
Wall area (sq ft) = Width (ft) × Height (ft) × Number of walls
Net area = Wall area − (Doors/windows × 21)
Rolls = ceil(Net area × (1 + waste) ÷ usable coverage)
- Standard US roll: 20.5 in × 33 ft ≈ 56 sq ft gross, about 50 sq ft usable after trimming top and bottom. A double roll is twice the length (≈100 sq ft usable) — better value, fewer seams to match.
- Pattern repeat is the vertical distance before the design repeats. No pattern: 5% waste. Small repeat (under 12 in): 15%. Large repeat (over 12 in): 25%.
- Strip check: each strip is ~20.5 in wide, so a 12-ft wall needs about 7 strips. If your wall height doesn't divide the roll length evenly, you lose a partial strip per roll — that loss is what the waste percentage covers.
- Dye lots matter: buy every roll at once from the same batch number. Two "identical" rolls from different lots can be visibly different on the wall.
Frequently asked questions
What is the difference between a single roll and a double roll?
A US single roll is 20.5 inches wide × 33 feet long (~56 sq ft). A double roll is the same width but 66 feet long (~112 sq ft). Double rolls cost less per square foot and mean fewer pattern matches to align.
What does "pattern repeat" mean?
The vertical distance before the wallpaper design repeats itself. With a 24-inch repeat, every strip must start at the same point in the 24-inch cycle, so you throw away the offcut between strips — that is the waste this estimator adds.
Why do I need extra for waste?
You trim a few inches top and bottom of every strip, and pattern matching discards the piece between repeats. Even pattern-free paper loses ~5% to trimming and mis-cuts.
My walls are different sizes — what do I enter?
Measure each wall (width × height), add the areas together, then enter the total as one wall with "1" for the number of walls.
Why subtract 21 sq ft per door or window?
A standard interior door with trim is about 21 square feet, and most windows are close to that. It is an approximation — for oversized windows, measure and subtract the real area instead.
Should I buy an extra roll just in case?
Yes — one spare roll is the cheapest insurance in wallpapering. A bad cut, a future patch, or a discontinued pattern will cost far more than one extra roll bought from the same dye lot.
What is a dye lot and why does it matter?
The batch number printed on the roll. Ink color shifts slightly between print runs, so two rolls with different lot numbers can show a visible seam. Buy all rolls together and check the numbers match.
Does this work for peel-and-stick wallpaper?
Yes — the area math is identical. Peel-and-stick usually comes in wider rolls (often 17.7 in × 33 ft or similar), so check the usable coverage on the package and pick the closest roll size.
How many strips do I get from one roll?
Divide the roll length by (wall height + a few inches of trim). A 33-ft single roll on 8-ft walls gives 3 full strips with waste — the leftover is rarely usable once pattern matching eats into it.
Do I paper behind heavy furniture or appliances?
Pros skip hidden areas like behind a built-in wardrobe to save paper, but keep one spare roll for future repairs. If the furniture might move one day, paper the whole wall.