How Much Wallpaper Do I Need for a Room? (2026 Guide)
Measure the perimeter, multiply by wall height, subtract doors and windows, then divide by usable roll coverage. Step-by-step math, a worked example and a chart for common bedrooms.
The wallpaper math, step by step
1. Measure the room perimeter
Perimeter = (length + width) × 2. For a 12×12 ft room: (12 + 12) × 2 = 48 ft.
2. Turn the perimeter into wall area
Multiply by the wall height: 48 × 8 = 384 sq ft.
3. Subtract doors and windows
A standard interior door is about 21 sq ft and a typical window about 15 sq ft: 384 − 36 = 348 sq ft. Adjust for bigger openings.
4. Add waste for pattern matching
Each strip is trimmed to line up the pattern, so usable coverage shrinks as the repeat grows. A seamless or small-repeat double roll delivers about 56 sq ft usable; a large repeat drops it to 40–50 sq ft. A ~15% allowance is typical — trust the label on the roll you buy.
5. Divide by usable coverage and round up
Rolls = (net area × 1.15) ÷ usable sq ft per roll, rounded up. Net 348 × 1.15 ≈ 400 sq ft; 400 ÷ 56 ≈ 7.2 → 8 double rolls. A US single roll covers about 28 sq ft; a double roll about 56 sq ft (roughly 20.5 in × 33 ft). Divide by the usable figure on your label.
Worked example: a 12×12 bedroom with 8-ft walls
Perimeter 48 ft × 8 ft = 384 sq ft, minus one door (21 sq ft) and one window (15 sq ft) = 348 sq ft. Add 15% for pattern matching ≈ 400 sq ft. 400 ÷ 56 ≈ 7.2, rounded up to 8 double rolls. With no pattern to match you can buy fewer: 348 ÷ 56 = 6.2 → about 7 double rolls.
Wallpaper needed for common bedrooms
| Room | Wall height | Net area (sq ft) | Double rolls |
|---|---|---|---|
| 10×10 | 8 ft | 284 | 6 |
| 10×10 | 9 ft | 324 | 7 |
| 12×12 | 8 ft | 348 | 8 |
| 12×12 | 9 ft | 396 | 9 |
| 12×14 | 8 ft | 380 | 8 |
| 12×14 | 9 ft | 432 | 9 |
| 12×16 | 8 ft | 412 | 9 |
| 12×16 | 9 ft | 468 | 10 |
Chart assumes one door (~21 sq ft) and one window (~15 sq ft) subtracted, 15% pattern allowance and 56 sq ft usable per double roll, rounded up. Large repeats add one roll.
When you need extra rolls
- Large pattern repeats — usable coverage drops to 40–50 sq ft per double roll; plan one more roll than the chart shows
- Sloped ceilings, dormers and bay windows — angled cuts waste more; add 15–20% instead of 15%
- First wallpaper job — a returnable spare roll is cheap insurance
Final tip
Buy all rolls from the same dye lot — the same pattern number in different lots can differ in color — and keep leftover strips labeled for repairs.
Estimating other materials for the same room? See how many tiles you need for a room or how much paint a 12×12 room takes.
FAQ
How much extra does a large wallpaper pattern repeat need?
With a repeat near 20 in you can lose up to 20 in of every 8-ft strip — roughly 20% of the roll. Usable coverage drops from ~56 to ~44 sq ft per double roll, so plan on 40–50 sq ft — 9 instead of 8 for the 12×12 room above.
Do I still add 10% after subtracting the door and window?
Keep one buffer, not two. Subtract the openings from the gross wall area first, then apply a single 10–15% allowance for cutting, pattern matching and mistakes. Rounding up to a full double roll usually provides that cushion, so don't stack another 10% on the pattern allowance. Buy one extra roll only for a large repeat or a first install.
How do I measure walls with sloped ceilings or eaves?
Measure each wall as its own section. For a gable or eave wall, multiply the width by the height up to where the ceiling starts, then add half the width × the additional rise for the triangle above. Measure dormers and bay-window faces one plane at a time, add the totals, and add 15–20% waste for angled cuts.
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