Wallpaper Calculator

How to Use the Wallpaper Calculator

Estimate exactly how many rolls of wallpaper you need to cover a room. The calculator converts your room dimensions into total wall area, subtracts doors and windows, adds pattern-repeat and waste allowances, then divides the result by one roll's usable coverage.

1. Enter room dimensions — room length, width, and wall height in feet. Measure floor to ceiling, and go wall-to-wall for the perimeter.
2. Specify doors and windows — standard door (3′ × 7′) and window (3′ × 5′) areas are subtracted from the total wall area.
3. Set wallpaper roll size — enter the roll width (in inches) and roll length (in feet). The default is a standard American single roll: 20.5″ wide × 33′ long, around 56 sq ft of coverage.
4. Set pattern repeat — enter the repeat distance in inches if your design has one. Use 0 for solid colours, textures, or random-match prints.
5. Set waste percentage — 10% is standard for plain or straight-match papers; use 15–20% for large drop-match patterns, uneven walls, or first-time installers.

About Wallpaper Estimating and How It Works

The core calculation is Net Wall Area = Perimeter × Height − (Doors + Windows). Perimeter equals 2 × (Length + Width), so a 12 × 14 ft room with 8-ft ceilings has 416 sq ft of gross wall area, minus about 21 sq ft for one door and one window, leaving roughly 395 sq ft of net wall area to cover.

Pattern repeat waste is the reason you cannot just divide net wall area by roll area. Patterned wallpaper is cut in strips that must align at the seams, so each strip is trimmed to a multiple of the repeat distance rather than the exact wall height. The usable length per strip is ceil(Wall Height / Repeat) × Repeat. For a 96-inch wall with a 21-inch repeat, each strip has to be cut to 105 inches, wasting 9 inches at every drop. That waste stacks up quickly across a room.

Waste allowance covers everything else: trimming the first strip to vertical, doorways cut with full-width strips, bubbles or torn edges, mistakes on internal corners, and dye-lot matching for touch-ups. A 10% buffer is industry standard; if you are learning, add 20% to avoid a second order at a different dye lot.

Examples

Example 1 — Bedroom, plain paper. A 12 × 12 ft bedroom with 9-ft ceilings has a perimeter of 48 ft and gross wall area of 432 sq ft. Subtract a door (21 sq ft) and window (15 sq ft) for 396 sq ft net. With 10% waste and a standard 56 sq ft US single roll: 396 × 1.10 / 56 ≈ 7.8 rolls — round up to 8 rolls, plus one spare for dye-lot protection.

Example 2 — Patterned, large repeat. The same room with a 24-inch pattern repeat and 9-ft (108″) walls means each strip is cut to 120″ (the next multiple of 24). That is 12 extra inches per strip, roughly 11% extra waste on top of the standard 10%, so budget around 20%. Rolls needed: 396 × 1.20 / 56 ≈ 8.5 — round up to 9 rolls.

Example 3 — Accent wall. One 14-ft wide × 9-ft tall wall is 126 sq ft. Minus a 15 sq ft window: 111 sq ft. With 10% waste: 111 × 1.10 / 56 ≈ 2.2 rolls — round up to 3 rolls. Using a double roll (113 sq ft of coverage) you could finish the job with just 2 doubles.

Square-Feet Workflow (Imperial)

If you already know wall area in square feet rather than dimensions, the wallpaper calculation simplifies. One US standard single roll covers about 56 sq ft total but only 30–36 sq ft after pattern repeat and waste, so the practical rule is Rolls = ceil(Wall Sq Ft × (1 + Waste%) / 30). A 400 sq ft wall area at 10% waste gives 400 × 1.10 / 30 ≈ 14.7, round up to 15 single rolls or 8 doubles. This square-feet shortcut matches the dimension-based calculation within one roll for most rooms and is what professional wallpaper estimators use when given measured area instead of room dimensions.

Metric / Imperial Conversions

European packaging is metric: rolls are typically 0.52 m (20.5″) wide by 10.05 m (33′) long, giving 5.23 m² (about 56 sq ft) per roll. To convert: 1 m = 3.281 ft, 1 m² = 10.764 sq ft. If your supplier gives roll length in meters, multiply by 3.281 to get feet before entering it into the calculator. If wall dimensions are in meters, multiply by 3.281 first or convert area in m² to sq ft by multiplying by 10.764. The wallpaper math itself is identical in either unit system — only the input units change.

Tips and When to Use

Use this wallpaper quantity calculator for any wall paper calculation, whether it is a single accent wall, a full bedroom, a stairwell, or a hallway. Always order all rolls in the same purchase to guarantee matching dye lots, and keep at least one unopened roll for future repairs. For rooms with lots of windows or angled ceilings, lean toward the higher waste allowance. If you are between rolls, round up — a leftover half-roll costs far less than re-ordering a single roll at a different dye lot. For small bathrooms or entryways, a double-roll (two bolts of standard length) is often the most economical choice.