How to Calculate Wallpaper
Published 2026-09-04
Multiply the total wall run by the wall height for square footage, add 15% for trimming and pattern matching, then divide by the usable coverage per roll — about 28 square feet. A 12 × 14 room at 8 feet needs about 17 rolls.
Wallpaper is the one wall covering where running short is genuinely expensive — a replacement roll from a later print run will not match what is already hung. That makes the estimate worth doing twice.
The formula
wall ft² = total wall run × wall height
with waste = wall ft² × 1.15
rolls = with waste ÷ 28 ft² usable per rollTwenty-eight square feet is usable coverage, not the figure on the label. The Wallcoverings Association puts a metric double roll at 56–58 ft² and an American double roll nearer 72 ft² — but between trimming the selvedge, squaring the first drop and matching the pattern, roughly half of that nominal area is lost on a typical room. Check which kind you are buying: the same “double roll” wrapper covers two quite different amounts of wall.
Our wallpaper calculator works from the 28 ft² usable figure and lets you set the waste percentage yourself.
Measuring the walls
Measure the perimeter with a tape at waist height and multiply by the height from baseboard to ceiling:
| Room | Perimeter | Height | Wall area |
|---|---|---|---|
| 12 × 14 bedroom | 52 ft | 8 ft | 416 ft² |
| 10 × 12 dining room | 44 ft | 9 ft | 396 ft² |
| 5 × 8 powder room | 26 ft | 8 ft | 208 ft² |
Change any measurement to update your estimate.
- Area to cover
- 368 ft²
- Exact amount
- 13.14 rolls
Worked example: the 12 × 14 bedroom
- Wall area: 52 × 8 = 416 ft²
- With 15% waste: 416 × 1.15 = 478 ft²
- Rolls: 478 ÷ 28 = 17 rolls
Round up, always. Seventeen rolls at 28 ft² of usable coverage is 476 ft², so a 16-roll order would leave you a strip short on the last wall.
Pattern repeat changes everything
The repeat is the vertical distance before the design starts again, printed on the roll label. Every strip has to be cut so its pattern lines up with the one beside it, and the offcut is wasted:
| Repeat | Add for waste |
|---|---|
| Random / free match | 10% |
| Under 6 in | 15% |
| 7–12 in | 18% |
| 13–18 in | 20% |
| Over 19 in | 25% or more |
A large repeat on a tall wall is the worst case: on a 9-foot wall with a 21-inch repeat, you may lose most of two feet from every strip.
If you are pricing the whole room, the paint calculator handles the ceiling and trim on the same measurements.
Do not deduct small openings
Subtract only genuinely large openings — a picture window, a wide doorway, a fireplace breast. Leave standard doors and windows in the calculation. You still need full-height drops either side of them, and the cut-outs rarely yield a piece big enough to use elsewhere.
Buy one dye lot, and buy it all at once
Every roll carries a pattern number and a run or dye-lot number, and the Wallcoverings Association is blunt about it: check every individual roll in the order for a matching run before you start. Colour drifts between print runs, and the difference is invisible in the shop but obvious on a wall under raking light. Check that every roll in the order shares a lot number, and buy the spare roll now rather than when you discover you need it — by then the lot will be gone.
Keep the offcuts
Store the leftover roll flat and dry with the lot number visible. When a section gets damaged in five years, a matching patch from the original lot is the only repair that will not show.