🖼️ Wallpaper Calculator

What This Calculator Does

This calculator tells you how many rolls of wallpaper a room needs. Enter the total length of the walls you are papering, the wall height, and the doors and windows, choose the roll type, and it converts the paperable area into a roll count with realistic usable coverage — not the optimistic number on the label.

Wallpaper punishes bad estimates twice: running short means hunting the same batch weeks later (often impossible), and pattern waste means the label's square footage never survives contact with a real wall. The calculation here uses the usable figures decorators actually plan with.

Wall Area, Openings, and Usable Coverage

The area math is familiar: total wall length × height, minus openings — a standard door removes about 21 sq ft and an average window about 15. A room with 40 linear feet of papered wall at 8 ft height has 320 sq ft gross; one door and one window bring it to 284 sq ft of paperable surface. So far it is paint math.

Coverage is where wallpaper diverges. A standard US single roll contains about 36 sq ft of paper, but trimming at top and bottom, plus pattern matching, reduces the honest usable figure to roughly 25-30 sq ft — the calculator's default of 28 splits the range. European rolls (the common 20.5″ × 33′ metric size) carry about 56 sq ft with proportional waste. Dividing 284 sq ft by 28 usable gives 10.1, and rolls only sell whole: 11 rolls. Rounding up is not caution — part-strips around windows and above doors still consume full-width cuts from the roll.

Pattern Repeats: Where the Paper Goes

The pattern repeat — printed on every label — is the vertical distance before the design recurs, and it is the single biggest variable in wallpaper waste. Adjacent strips must align, so each strip is cut not to the wall height but up to the next repeat boundary above it: with 8-ft walls and a 24-inch repeat, strips are cut in 2-ft increments, and up to 23 inches of each can be trimmed away. Small repeats (or free-match papers with none) hang close to the theoretical coverage; bold 20-30 inch repeats can push effective waste past 25%.

Match type matters alongside repeat size. Straight match patterns align at the same height on every strip; drop match patterns offset alternate strips by half a repeat, which sounds worse but often wastes slightly less with careful cutting (decorators sometimes cut alternating strips from two rolls to optimize). Random match — textures and verticals — wastes least of all. For a large-repeat paper, the practical adjustment is to plan on the low end of usable coverage (~25 sq ft per single roll) or simply add one roll to the calculated count; the pattern you fell in love with is worth the honest arithmetic.

Buying and Hanging Without Regret

Batch numbers are wallpaper's dye lots: rolls printed in different runs differ subtly, and a wall reveals it at every seam. Buy the full quantity plus one spare roll at once, all matching batch numbers, and keep the spare — it insures against a ruined strip during hanging and provides repair material for years (a papered wall's damage is otherwise unfixable without a visible patch). If a shortfall does happen, batch-match with the supplier before accepting a different lot.

Two planning notes finish the job well. First, count strips as a sanity check: strips needed = total wall length ÷ paper width (a 20.5″ paper covers 1.7 ft per strip), and strips per roll = roll length ÷ cut-strip length; the two together confirm the roll count from a different direction. Second, walls in poor condition need lining paper or serious prep — wallpaper telegraphs every bump paint would forgive. The calculator supplies the count; buying it in one batch with one spare supplies the peace of mind.

Quick Tips

• Area = wall length × height − ~21 sq ft per door, ~15 per window.
• Usable coverage ≈ 28 sq ft per US single roll (label says 36); big repeats mean less.
• Buy every roll plus one spare from the same batch number.
• Random-match papers waste least; large drop-match repeats waste most.

Frequently Asked Questions

How many rolls of wallpaper do I need?

Compute the wall area (total wall length x height, minus about 21 sq ft per door and 15 per window) and divide by the usable coverage per roll — around 28 sq ft for a standard US single roll after trimming and pattern waste. A 40-ft wall run at 8 ft with a door and window needs about 11 rolls.

Why is a roll's usable coverage less than its printed size?

Trimming at ceiling and baseboard, matching the pattern between strips, and the part-strips around openings all consume paper. A roll with ~36 sq ft of paper realistically hangs about 25-30 sq ft — and large pattern repeats push waste higher.

What is a pattern repeat and why does it matter?

The vertical distance before the design repeats. Every strip must align with its neighbor, so you cut each strip to the next repeat boundary — a 20-inch repeat can waste up to 20 inches per strip. Bigger repeats mean fewer usable strips per roll.

Should I buy all rolls at once?

Yes, from the same batch (lot) number. Wallpaper batches vary subtly in color, and a mismatched roll shows as a visible seam-to-seam shift. Buy the full count plus one spare roll from one batch.

Honest Coverage, Free to Use

This calculator runs entirely in your browser, using realistic usable-coverage figures the moment you type. It needs no account or download and works on any device. Like every tool here, it is free to use as often as you like.

Related Tools

For more wall math, the paint calculator covers the painted rooms, the drywall calculator handles the walls beneath, and the square footage calculator measures anything.