Wallpaper Calculator

Doors and Windows Do More Than You'd Guess

A room's gross wall area — perimeter times height — overstates how much wallpaper is actually needed, because doors and windows don't get papered. Skip the deduction and you'll overbuy; skip the waste allowance for pattern matching and seam trimming and you'll run short mid-room. This calculator accounts for both, using standard door and window size assumptions to net out the paperable area.

The Formula

Wall Area = Perimeter × Height − Door/Window Deductions
Rolls Needed = ceil((Wall Area × (1 + Waste%)) / Roll Coverage)

Deductions assume a standard door at roughly 21 sq ft and a standard window at roughly 15 sq ft — reasonable defaults for typical residential openings, though an unusually large window or French doors would need manual adjustment.

Where This Calculation Matters

Buying matched-batch rolls — wallpaper is dye-lotted, so ordering enough in one purchase avoids a mismatched pattern from a later reorder.
Pattern repeat waste — large-repeat patterns often need more than the standard 10% waste allowance to align seams correctly; the waste percentage input lets you adjust for that.
Comparing roll sizes across brands — European and domestic rolls come in different standard coverage amounts, and this formula normalizes any roll size against the room's actual need.
Budgeting an accent wall vs. a full room — the same formula scales down cleanly for a single feature wall by adjusting the perimeter input.

Rolls Needed by Room Size

For a square room with 9 ft walls, one standard door, one standard window, and a 10% waste allowance:

Rolls needed by room size, 9 ft walls, 1 door, 1 window, 10% waste, 30 sq ft/roll
Room size	Net wall area	Rolls needed
10 ft × 10 ft	324 sq ft	12
12 ft × 12 ft	396 sq ft	15
14 ft × 14 ft	468 sq ft	18
16 ft × 16 ft	540 sq ft	20

How to Use This Calculator

Enter Room Length, Room Width, and Wall Height (ft).
Enter the Number of Doors and Number of Windows to deduct from the paperable area.
Adjust Roll Coverage if your specific wallpaper's label states a different figure than the 30 sq ft default.
Adjust Waste % if your pattern has a large repeat needing extra allowance (defaults to 10%).
Select Calculate to see the number of rolls needed, rounded up to a whole roll.

Related Calculations

Comparing paint instead of wallpaper? Check the Paint Coverage Calculator, or budget the full room refresh with the Remodeling Cost Calculator.