Wallpaper Calculator
Estimate wallpaper rolls using whole drops, trim and straight pattern repeats, with clear assumptions.
This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.
Wallpaper Calculator counts complete drops and whole rolls for equal-height walls, including trim, straight pattern repeats and your optional whole-roll spares.
How to use it
- 1Enter each wall width, their shared height and the actual continuous roll dimensions.
- 2Choose free or straight match and supply trim, repeat when applicable and any starting loss.
- 3Review drops per wall, cut length and full rolls, then save the JSON estimate if useful.
Example
- Input
- 5 × 2.4 m wall; 0.5 × 10 m roll; 10 cm total trim; 60 cm straight repeat; no start loss or spares.
- Output
- 10 drops cut at 3 m; 3 full drops per roll; 4 rolls.
Offset/half-drop and A/B designs are outside this full-drop model.
What happens to your data
Wall widths, roll dimensions and cutting allowances stay in the browser. Downloading creates a local JSON report containing the measurements and full-drop assumptions; no measurements are uploaded or persisted by the tool.
Last updated October 2026
Wallpaper is bought in continuous rolls but installed in vertical drops. Dividing wall area by roll area can miss a practical restriction: a short piece left at the end of a roll may be too short to cover the wall. This wallpaper calculator counts complete drops, adds your top-and-bottom trim, accounts for a straight pattern repeat when selected, and then rounds up complete rolls.
Enter up to 20 separate wall widths that share one height and use one product. Each wall rounds up to its own full-width drop count before the totals are pooled. You can see every wall's contribution, the cut length, the complete drops available from a roll and the reason a roll may leave a short remnant. Doors and windows are deliberately retained in the full-height estimate instead of being subtracted as if every remaining square centimetre were interchangeable.
How it works
For each wall, divide its width by the actual usable wallpaper width and round up to a full drop. A 5 m wall and a 0.5 m roll require 10 drops. A 5.01 m wall requires 11. Separate walls are rounded separately because this estimate does not reuse a narrow edge offcut from one wall on another. All supplied walls must have the same height; otherwise group them into separate estimates. This is a conservative full-drop model, not a drawing of seam locations or a solution for every corner.
Add the total trim allowance to the shared wall height. The trim field is the combined top and bottom amount per drop: entering 10 cm means 10 cm total, not 10 cm at each end. For free match, this height-plus-trim is the cut length. For straight match, round the height-plus-trim up to a whole multiple of the vertical pattern repeat. For example, 2.4 m height plus 10 cm trim gives 2.5 m; with a 60 cm repeat, the cut length becomes 3 m. The extra 0.5 m is shown as pattern-related length per drop.
The start-of-roll matching-loss field is separate. Deduct that amount from each roll before counting complete drops. It can reserve the initial motif alignment or a known unusable end; the program cannot inspect where the pattern begins on your actual roll. After that deduction, divide usable roll length by cut length and round down. Ten usable metres divided by three metres yields three full drops and a one-metre remnant per fully cut roll. That short remnant is not combined with another short piece to invent a fourth full drop.
Add the wall drop counts, divide by the complete drops per roll and round up to whole rolls. Optional extra whole rolls are then added explicitly. There is no automatic 10% or other hidden waste allowance. The result separates the base rolls from your chosen spares. Unused full-drop capacity describes how many more complete cuts the purchased rolls could theoretically provide; it is not a promise about usable offcuts after installation. The displayed short remnant assumes a roll is cut into its maximum full-drop count. A partly used final roll may retain a longer continuous length.
Metric mode uses metres for wall widths, shared height, roll width and roll length, and centimetres for trim, pattern repeat and starting loss. US customary mode uses feet for walls and continuous roll length, and inches for usable roll width and the small cutting allowances. Conversions and ceiling/floor decisions use exact decimal fractions. Changing systems clears dimensional values instead of silently treating a centimetre value as inches. Every edit clears the previous result and download. In free-match mode, a hidden pattern-repeat value is ignored and omitted from the export.
Only free and straight matches are supported. Offset or half-drop patterns, paired A/B rolls, murals, reverse-hanging requirements, stair walls and sloped ceilings need a product-specific plan. The manufacturer explains how its match works; selecting straight match for a half-drop product does not convert it into one. Use actual usable width and continuous length from the label, because a sales description such as single roll or double roll may not identify the physical dimensions reliably. Check the product's hanging and batch guidance before ordering.
Inputs accept plain decimals with up to six places. The software supports up to 20 wall widths, one per line, and refuses a drop that does not fit into the usable roll length. It caps a dimension at 10,000 metres equivalent, total drops at 1,000,000, full drops per roll at 1,000,000, extra rolls at 10,000 and total rolls at 1,000,000. It does not upload or store measurements. The optional JSON estimate records active wall and roll inputs, per-wall drops, cut length, roll quantities and assumptions for later checking.
Worked example: A straight repeat changes the number of usable drops
- Input
- Wall 5 m wide × 2.4 m high; roll 0.5 m wide × 10 m long; 10 cm combined trim; 60 cm straight repeat; zero start loss or spare rolls.
- Result
- 10 drops; 2.5 m height with trim; 3 m cut length; 3 full drops per roll; 4 rolls; 2 unused full-drop slots and a 1 m remnant per fully cut roll.
With the same inputs and free match, each 2.5 m cut fits four times per roll, giving three rolls. No doors, windows or reusable edge offcuts are deducted.
Common use cases
- Comparing free-match and straight-match cutting quantities for explicitly measured rolls
- Estimating a group of equal-height walls while keeping each wall's rounded drop count visible
- Checking whether a small change in repeat or trim reduces the full drops obtainable per roll
- Saving the actual product dimensions and chosen starting-loss or spare-roll assumptions with an order estimate
Frequently asked questions
Should I subtract doors and windows from the wall area?＋
Not in this full-drop calculator. Openings do not necessarily eliminate a full-height drop, and matching around them can require material. Enter the complete wall widths. An installer may be able to reuse short pieces, but that needs a layout-specific cutting plan that this estimate does not make.
Is pattern repeat the same as the half-drop offset?＋
No. Straight match aligns adjacent strips at the same height. An offset match shifts the alignment between adjacent strips. This tool supports free and straight match only; it does not interpret a two-number repeat/offset label or produce an alternating half-drop cutting sequence.
Why did one extra centimetre add a whole roll?＋
Purchasing is discrete. A width increase can require another full drop, while a height or repeat increase can reduce the complete drops cut from each roll. Both boundaries occur before roll count rounding. The result exposes the intermediate numbers so you can identify which boundary changed.
Can walls with different heights share a calculation?＋
No. The entered walls share one height and one cut length. Separate estimates avoid pretending that a short offcut can be used on an unrelated tall wall. Mixed-height cutting optimization could sometimes use less material, but is not performed here.
What start-of-roll matching loss should I enter?＋
Use the amount needed to begin at your chosen motif or remove an unusable end, based on the actual product and installation plan. The value is deducted from every roll before full drops are counted. Zero means you deliberately reserve none; it is not a guarantee that every roll starts at the desired pattern point.
Does the tool recommend a spare-roll percentage?＋
No. It reports the base full-roll quantity and lets you add a chosen number of whole spare rolls. The amount appropriate for mistakes, damage, future repairs or batch matching depends on the product and project. Follow the supplier's guidance rather than treating the example as a universal allowance.
How does wallpaper estimating differ from paint or tile estimating?＋
Paint uses product coverage per coat, while area-based tile purchasing uses dimensions or manufacturer box coverage. Wallpaper also needs full-length pieces and sometimes pattern alignment, so area alone is insufficient. The related Paint Coverage and Tile Calculators expose the assumptions relevant to those materials.
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