Wallpaper Calculator
Wallpaper rolls = strips needed ÷ usable strips per roll; each strip is the wall height plus trim, rounded up to whole pattern repeats. A 50 ft perimeter with 9 ft walls, 20.5 in × 33 ft rolls and an 18 in repeat needs 30 strips at 3 per roll: 10 rolls. To paint instead, see the Wall Paint Calculator.
How it's calculated: Rolls = strips (perimeter ÷ roll width, rounded up) ÷ strips per roll (roll length ÷ strip length, rounded down), rounded up.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Strip length = wall height + trim; with a repeat, round up to a whole number of repeats
Strips per roll = ⌊ roll length ÷ strip length ⌋
Strips needed = ⌈ perimeter ÷ roll width ⌉ − ⌊ openings ÷ 2 ⌋
Rolls = ⌈ strips needed ÷ strips per roll ⌉
Run the calculation to see each step with your own numbers.
50 ft perimeter, 9 ft walls, 20.5" wide × 33 ft rolls, 18 in pattern repeat, no openings credited.
Strip length = 9.33 ft → 10.5 ft (7 × 18 in repeats)
Strips per roll = ⌊33 ÷ 10.5⌋ = 3
Strips needed = ⌈50 ft ÷ 20.5 in⌉ = 30 → rolls = ⌈30 ÷ 3⌉ = 10
- Rectangular room, full-height drops. A large pattern repeat wastes the offcut at the top of each strip — the calculator rounds each strip up to a whole repeat, which is what a paperhanger does.
- Openings are credited at half a strip each — conservative; a big picture window saves more, a small window less.
- A 'double roll' is the common US package (~56 sq ft, ~33 ft long). Single rolls are half that. Enter the actual roll length from the label.
- Paste, liner and trim are separate.
- Why does the pattern repeat matter so much?
- Every strip has to start at the same point in the pattern to match its neighbour, so you cut off and discard part of the top of each strip — up to one full repeat. A 24-in repeat on a 9-ft wall can cut usable strips per roll from 3 down to 2.
- Single roll or double roll?
- US wallpaper is usually sold as a double roll — about 56 ft² and 33 ft long — even though it is priced as two singles. Enter the actual roll length printed on the label, not '1 roll'.
- Should I order extra?
- Yes, and from a single dye lot. Buy at least one spare roll: patterns get discontinued, and a later roll from a different lot will not match on the wall.
- How many rolls of wallpaper do I need?
- Divide the total wall length by the roll width for the number of strips, work out how many full-height strips one roll gives after matching the pattern, then divide. A 50 ft room with 9 ft walls and an 18 in repeat needs 10 double rolls.
Estimating method
Standard paperhanger estimating: usable strips per roll = ⌊roll length ÷ strip length⌋ with the strip rounded up to a whole pattern repeat. Matches Wallpaper Installers Association / manufacturer roll-coverage guidance.
About the Wallpaper Calculator
The Wallpaper Calculator works out how many rolls a room needs, accounting for the pattern repeat — the biggest source of waste. With a repeat, every strip is cut to a whole number of repeats so the pattern lines up, which can drop the usable strips per roll from three to two. Enter the wall perimeter and height, the roll size from the label, and the repeat (0 for a plain paper).
What you enter
- Total wall length (perimeter) — Add up the width of every wall you're papering.
- Wall height
- Roll width — US rolls are ≈ 20.5" wide; European rolls ≈ 20.9" (0.53 m).
- Roll length — US double roll ≈ 33 ft; European roll ≈ 33 ft (10.05 m). Check the label.
- Pattern repeat — Vertical distance the pattern repeats. 0 for a plain / random-match paper.
- Trim allowance per strip — Extra length cut off top and bottom of each strip — ≈ 4 in total.
- Doors / windows (each ≈ half a strip saved)
What you get back
- Strips (drops) needed — the exact result of the calculation.
- Usable strips per roll — the exact result of the calculation.
- Rolls to buy — Buy all rolls from one batch/dye lot. Keep a spare — patterns are discontinued.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Wall Square Footage Calculator — Wall area for one or more walls, with openings deducted.
- Paint Calculator — Paint in gallons or litres for a project from surface area and coats.
- Wall Paint Calculator — Paint for walls only, with doors and windows deducted.
- Shiplap Calculator — Shiplap boards and lineal feet for a wall area.
Part of the Walls calculators.