Calculateur de papier peint

Wallpaper Calculator

Use this wallpaper calculator to estimate how many rolls you need for a room and how much the project may cost. It accounts for wall dimensions, roll size, pattern repeat, and waste — so you can place a single accurate order and avoid running short or stockpiling unused rolls.

How Roll Quantity Is Calculated

The calculation works in four steps:

1. Total gross wall area = Room perimeter (ft) x Wall height (ft)
2. Net wall area = Gross area minus large openings (each door is roughly 21 sq ft; each window roughly 15 sq ft)
3. Usable coverage per roll = Roll width (ft) x Roll length (ft) x (1 - waste fraction)
4. Rolls needed = Net wall area / Usable coverage per roll, rounded up to the next whole roll

Rolls Needed = ceil( Net Area / (Roll Width x Roll Length x (1 - Waste Factor)) )

A standard US double roll is 27 inches wide by 54 feet long — about 60 sq ft gross. With 10% waste, usable coverage is 54 sq ft per double roll.

Worked Examples

Example 1 — Simple living room, no pattern: Room is 12 ft x 14 ft, 8 ft ceilings, two doors, two windows. Perimeter = 52 ft. Gross area = 52 x 8 = 416 sq ft. Subtract 2 doors (42 sq ft) + 2 windows (30 sq ft) = 344 sq ft net. Using double rolls at 54 sq ft usable (10% waste): 344 / 54 = 6.37 — order 7 double rolls.

Example 2 — Bedroom with 18-inch pattern repeat: Room is 11 ft x 13 ft, 9 ft ceilings, one door, one window. Perimeter = 48 ft. Gross area = 432 sq ft. Subtract 36 sq ft = 396 sq ft net. An 18-inch repeat on a 9-ft wall wastes about 3 inches per strip — effective waste factor rises to 18%. Usable per double roll = 60 x 0.82 = 49.2 sq ft. Rolls needed = 396 / 49.2 = 8.05 — order 9 double rolls.

Example 3 — Feature accent wall only: Single 12-ft wall at 8 ft = 96 sq ft gross. One small window = 15 sq ft. Net = 81 sq ft. With 10% waste: 81 / 54 = 1.5 — order 2 double rolls.

Wallpaper Roll Reference Table

When to Use This Calculator

• Planning a full-room wallpaper installation and budgeting material cost before ordering
• Estimating waste and rolls for a large pattern repeat before committing to an expensive designer paper
• Comparing cost per square foot between single rolls and double rolls of the same wallpaper
• Calculating material needed for a single accent or feature wall without over-ordering
• Verifying an online estimate from a retailer to catch errors before placing a large order

Common Mistakes

1. Measuring only one wall height. Ceiling height often varies by 1-2 inches across a room. Measure at several points and use the tallest measurement — cutting strips to the shortest height will leave gaps at the ceiling on uneven walls.
2. Forgetting to order from the same dye lot. Wallpaper is printed in batches, and dye color varies slightly between lots. If you run short and reorder, the new rolls may not match. Always order all rolls for a project at once, and buy one extra.
3. Applying a single waste percentage to all patterns. A straight-match small pattern may need only 8-10% waste; a 24-inch half-drop repeat can require 22-25% waste. Using a flat 10% for a large repeat will almost certainly leave you one or two rolls short.
4. Treating a US single roll and a US double roll as interchangeable. Many US wallpapers are sold physically as double rolls but labeled and priced as single rolls. Verify actual length before plugging numbers into the formula — dividing by single-roll coverage when your rolls are actually double will produce estimates half the size you need.

Real-World Applications

Interior designers routinely run these calculations for clients before finalizing wallpaper selections, since switching to a different roll size or pattern repeat mid-project can alter material costs by $200-$400 in a standard bedroom. Contractors bidding commercial jobs — hotel corridors, restaurant dining rooms — apply the same formula scaled to hundreds of linear feet, where even a 5% error in the waste factor changes the material budget significantly. DIY homeowners benefit most from catching the dye lot and extra-roll requirements before their first trip to the store, since finding a matching lot months after the initial project can be impossible.

Tips

1. Buy at least one extra roll from the same dye lot — save it labeled with the room name for future repairs around outlets, corners, and inevitable scuffs.
2. Confirm the actual roll width and length from the manufacturer’s product page, not just the store listing, before entering numbers into the calculator.
3. For pattern repeats over 12 inches, add the waste percentage before calculating — do not rely on the calculator’s default 10% if your pattern is large.
4. Remove all existing wallpaper before hanging new — papering over old paper traps moisture and causes the new paper to bubble and peel within months.
5. Apply a wallpaper primer (sizing) to the wall after removal and before hanging — it prevents the adhesive from soaking into drywall and makes future removal far easier.
6. On peel-and-stick wallpaper, measure twice and install slowly — repositioning after pressing firmly onto an unpainted drywall surface can tear the paper face.