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Wallpaper Calculator

Number of wallpaper rolls for a room, accounting for strip width, pattern repeat and openings.

How this is calculated

Strips = (perimeter − door widths − ½ window widths) ÷ roll width, rounded up. Drop = wall height + 4 in trim (rounded up to the pattern repeat). Rolls = strips ÷ strips per roll.

Wallpaper is hung in vertical strips, so the roll count depends on your roll size and pattern repeat — not just wall area. This calculator works out the strips, the drop length with pattern allowance, strips per roll and the final roll count.

Results are estimates for planning purposes only. Real-world quantities depend on site conditions, materials and workmanship. Always verify measurements, follow local building codes and confirm quantities with your supplier or a qualified professional before ordering or building.

About the Wallpaper Calculator

Wallpaper math is trickier than paint math: rolls come in fixed widths and lengths, and patterned paper wastes a repeat on every strip. This calculator converts wall dimensions into the number of strips (drops), how many strips each roll yields, and total rolls to buy — with the pattern repeat accounted for.

How to use

  1. Enter each wall width and the ceiling height — all four walls for a room, or just one for an accent wall.
  2. Subtract large openings, or leave them in: papering around windows wastes the strips anyway.
  3. Enter the roll width (20.5 inches is standard) and roll length from the product listing.
  4. Enter the pattern repeat in inches — zero for plain or random-match paper. It is printed on the label.
  5. Order all rolls from the same dye lot (batch number) so the color matches.

Understanding your results

Strips are the vertical drops needed to cover the wall width. Strips per roll shows how many full-height drops each roll yields after the repeat is accounted for. The roll count is strips divided by strips per roll, rounded up. The waste note separates pattern-matching allowance from actual wall coverage.

How the calculation works

Strips are wall width divided by roll width, rounded up. Each strip needs wall height plus one pattern repeat, so strips per roll are roll length divided by that cut length, rounded down. Total rolls are strips divided by strips per roll, rounded up. Example: a 12-foot wall needs 8 strips; with 8-foot ceilings and a 12-inch repeat, a 33-foot roll yields 3 strips — 3 rolls cover the wall.

Wallpaper Calculator FAQs

A US single roll covers about 30 square feet of usable wall after trimming, and a double roll about 60 — but pattern repeat reduces this in practice. The honest way to estimate is strips per roll, which is what the calculator does: a 33-foot roll on 8-foot walls with a 12-inch repeat yields only 3 strips. Always calculate from your wall height, not the nominal coverage.
Pattern repeat is the vertical distance before the design repeats — commonly 12 to 24 inches. Each strip must be cut so the pattern aligns with its neighbor, which wastes one repeat per strip on average. A large repeat on a short wall is the worst case: you can lose a third of every roll. Random-match and plain papers have no repeat and waste the least.
Order one extra roll beyond the calculated count for rooms with many cuts, and always keep one unopened roll after the job for future repairs. Wallpaper dye lots vary noticeably between batches, and a pattern discontinued next year makes a damaged strip unfixable. The extra roll is cheap insurance.
Yes, over clean, smooth painted walls in good condition — prime first with a wallpaper primer for the best adhesion and easiest future removal. Do not hang over glossy oil paint without sanding and priming, and never over peeling or textured paint. Fresh paint should cure at least 30 days before papering.
Peel-and-stick is more forgiving for beginners since you can reposition it, and it suits renters because it removes cleanly. Traditional pasted paper is more durable, handles textured walls better and offers far more designs. For a long-term installation in a bathroom or high-traffic area, pasted paper is the better investment.
Nabil Sharif, founder of CalcDune

Written by

Nabil Sharif

Founder of CalcDune — a free library of 137 online calculators for finance, health and everyday math. Every calculator shows the formula behind its result, so you can see exactly how your numbers are worked out.

More articles by Nabil →

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