Free project planning tool

Wallpaper Calculator

Estimate complete rolls from strip geometry instead of relying on nominal roll area, which can overstate usable coverage when a pattern must align.

Formula reviewedJuly 24, 2026Inputs stay on your device

Enter your measurements

US customary units

Combined wall width

Add the widths of every wall receiving this wallpaper.Maximum wall height

Use the tallest point when walls vary slightly.Roll width

Use the trimmed width printed on the product label.Roll length

Enter the usable length of one purchasable roll.Vertical repeat (straight match)

Enter zero for random match. Offset and drop matches need a verified cut-length override below.Drop-match cut length override

For half-drop or multiple-drop designs, enter the effective strip cut length from the product layout or installer; otherwise leave zero.Trimming allowance per strip

Spare strip allowance

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Calculated estimate

rolls

Wallpaper to buy

Required wall strips24

Planned strips with allowance27

Aligned cut length100 in

Full strips per roll3

Live planning viewSchematic · not to scale

Combined wall width40 ftMaximum wall height8 ftRoll width20.5 in

Wallpaper to buy9 rolls

Confirm whether the seller packages single rolls as a double-roll bolt, and order every roll from the same production run when possible.

CalcurHome project estimate

Wallpaper Calculator

Entered measurements

Combined wall width: 40 ft
Maximum wall height: 8 ft
Roll width: 20.5 in
Roll length: 33 ft
Vertical repeat (straight match): 0 in
Drop-match cut length override: 0 in
Trimming allowance per strip: 4 in
Spare strip allowance: 10 %

Estimate

9 rolls

Wallpaper to buy

Required wall strips24

Planned strips with allowance27

Aligned cut length100 in

Full strips per roll3

24 wall strips become 27 planned strips after the entered spare allowance, requiring 9 complete rolls.

Confirm whether the seller packages single rolls as a double-roll bolt, and order every roll from the same production run when possible.

Planning estimate only. Verify quantities, local prices, codes and structural decisions before purchase or construction.

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What does the wallpaper calculator calculate?

Divide the total wall width by the roll width to find required strips. Add trimming allowance to wall height, round that cut length up to the pattern repeat, and determine how many strips each roll yields. Apply a spare allowance, then round the required roll count up.

Wallpaper rolls from aligned strips

Rolls = ceiling[ceiling(wall width ÷ roll width) × spare factor ÷ floor(roll length ÷ effective matched strip length)]

Each strip spans wall height plus trimming room. Straight matches round that cut to the next vertical repeat. For half-drop or multiple-drop paper, the verified cut-length override replaces that shortcut. Whole-strip and whole-roll rounding prevents unusable fractions from being counted.

How to measure for an accurate estimate

Measure each wall horizontally at the ceiling and base, then use the longer width when the room is not square.
Use the greatest wall height and include sloped, stepped, or unusually tall sections as separate calculations.
Read roll width, usable length, match type, vertical repeat, and any offset-match layout from the exact product specification.
Do not automatically deduct ordinary doors and windows; strips around openings still require full-height pattern alignment.

Forty feet of eight-foot wall

Walls total 40 feet wide and 8 feet high. Rolls are 20.5 inches by 33 feet, with no repeat, 4 inches of trim, and 10% spare strips.

Twenty-four measured strips become 27 planned strips. Each 100-inch cut allows three strips per roll, so 9 complete rolls are required.

Before you purchase material

Confirm whether the listed package is a single roll, double-roll bolt, or another manufacturer-specific unit.
Buy matching run or lot numbers because color can vary enough between production batches to show at seams.
Inspect the first rolls before cutting, and retain labels until the pattern, color, and quantity are verified.
Follow the manufacturer’s surface preparation, primer, adhesive, booking, and pattern-match instructions.

Common questions

Should I subtract doors and windows from wallpaper?

Usually not for a strip-based estimate. Wallpaper above, below, and beside an opening still comes from full pattern-aligned drops. A professional may reuse large offcuts, but deducting every opening before layout can leave the project short.

How does pattern repeat change the roll count?

A straight vertical repeat rounds each strip to a matching point, leaving less usable roll length. Half-drop and multiple-drop layouts alternate pattern positions and can use more paper; enter a verified effective cut length from the product instructions or installer.

What does a double roll of wallpaper mean?

Wallpaper may be priced as a single-roll unit but packaged and shipped as a larger double-roll bolt. Dimensions and retail conventions vary, so use the usable width and length printed for the actual purchasable package, then confirm ordering units.

How much extra wallpaper should I order?

Ten percent is a practical planning allowance for damaged strips, mistakes, and later repairs, but complex rooms and large repeats can need more. Manufacturer instructions and an installer’s layout should control for expensive, handmade, or discontinued papers.

Sources and reference standards

Wallcoverings Association — Standard Installation of Residential WallpapersIndustry installation guidance for measuring, trimming, pattern matching, roll sequencing, and checking the manufacturer’s instructions.

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