Wallpaper Calculator
Pattern repeat is what makes wallpaper estimates wrong.
Wallpaper Calculator
Drops = ceiling(wall width / roll width); cut length = wall height + repeat; rolls = ceiling(drops / drops per roll).
Calculated instantly
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What This Calculator Does
The Wallpaper Calculator estimates rolls from the wall run, wall height, roll size, and pattern repeat. It counts whole vertical drops rather than dividing wall area by roll area, because pattern matching and trimming mean a roll rarely delivers its full printed coverage.
How It Works
The wall width is divided by the roll width to find how many vertical drops are needed, rounded up. Each drop is cut to the wall height plus one pattern repeat, which is the worst case for aligning a straight match. The roll length is divided by that cut length to find how many drops fit on one roll, rounded down. Rolls required is the drop count divided by drops per roll, rounded up. Areas are shown for reference only.
Example
A wall 12 ft wide and 9 ft high with a 20.5 in wide, 33 ft long roll and a 12 in repeat needs ceil(12 / 1.708) = 8 drops. Each cut is 9 + 1 = 10 ft, so 33 / 10 = 3 drops fit per roll. Eight drops divided by 3 gives 3 rolls, even though the 108 sq ft wall is less than the 56.4 sq ft printed on one roll times three.
Formula
ceiling(wall width / roll width in feet)wall height + pattern repeat in feetfloor(roll length / cut length per drop)ceiling(drops needed / drops per roll)Reading the Results
Drops needed
Whole vertical strips across the wall run, rounded up. A partial strip at the end still consumes a full drop.
Drops per roll
How many cuts fit in one roll after allowing one repeat for matching. It is rounded down because a partial cut cannot be used as a full drop.
Rolls required
The number to order before adding a spare. It assumes a straight match and a simple rectangular wall; a drop match, many corners, or a large motif can need more.
Sources and References
ASTM F793 - Standard Classification of Wall Covering by Use Characteristics
Wallcovering performance classes
Useful for choosing a covering suited to the room, not for estimating quantity.
Wallcoverings Association - installation and estimating guidance
Drop counting and pattern match allowances
Industry guidance confirms that pattern repeat and match type, not wall area alone, drive roll counts.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
What is a pattern repeat and why does it add waste?
The repeat is the distance before the pattern starts again. Adjacent drops must be shifted so the motif lines up, which means each cut needs up to one extra repeat of length. A 24 in repeat on a 9 ft wall effectively makes every drop 11 ft for cutting purposes.
Should I subtract windows and doors from the wall area?
No. Drops run from ceiling to floor past openings, and the offcut above or below a window is rarely long enough to reuse. Subtracting openings is the most common reason an estimate comes up short.
What is the difference between a straight match and a drop match?
A straight match lines up at the same height on every drop. A drop match, also called an offset match, shifts by half a repeat on alternate drops and can waste more. This calculator assumes the simpler straight match, so add a roll for an offset pattern.
Do I need to add a spare roll?
It is wise if the budget allows. Dye lots change, and a future repair may not match. Keep one unopened roll with the batch code written on it, especially in a room with heavy traffic or plumbing that might need a patch.
Can I use this for lining paper?
Yes, set the pattern repeat to zero. Lining paper has no match, so cut length equals wall height and the estimate becomes a straightforward drop count. Still round up, because damaged edges and trimming consume length.