Wallpaper roll & pattern calculator
This calculator turns a room's walls into the one number a wallpaper shopper actually needs — how many rolls to buy — while handling the two things cheap calculators get wrong: the pattern repeat and the difference between a straight and a drop match.
It works the way professional decorators do: in drops. A drop is a single floor-to-ceiling strip of paper. The tool counts the drops each wall needs, works out how many drops you get from one roll, then converts that into whole rolls, with a waste buffer and a spare you can adjust.
How many rolls of wallpaper do I need?
Start with the wall, not the roll. Add each wall's width and your ceiling height, and the calculator finds the drops per wall by dividing the wall width by the roll width and rounding up — a part-width strip is still a whole drop off the roll.
A standard 53 cm × 10 m roll gives about four full drops on a 2.4 m ceiling once you allow for trimming, so it covers roughly four drops' worth of wall. Doors and windows shave drops off the total; the pattern repeat adds length to every drop. The calculator keeps all of this straight and gives you a roll count you can take to the shop.
How the calculator works
Enter the room, choose your roll and pattern, then read the rolls to buy from the results panel. Every figure updates as you type, and nothing leaves your browser.
Five steps to your roll count
- Choose units and currencyPick metric (metres and centimetres) or imperial (feet and inches). Set a currency if you want a cost.
- Enter the roomSet the ceiling height and add each wall's width. The tool shows the drops per wall as you type.
- Add doors and windowsSet how many doors and windows there are and their sizes. They reduce the drops you need.
- Set the roll and patternChoose the roll width and length, enter the pattern repeat (0 for plain), and pick straight or drop match.
- Set paper, waste and sparesChoose the paper type for a paste recommendation, slide the waste buffer, and note any rolls you already have.
- Read the resultsRead the rolls to buy, paste packets and cost. Download a PDF buying list or export a CSV to bring to the shop.
Pattern repeat and match type
The pattern repeat is the vertical distance before the design starts again — it is printed on the roll label. For patterned paper, every drop has to be cut to a whole number of repeats so the design lines up across seams, which makes each drop longer than the bare wall height.
How the pattern lines up across the seam matters even more. A straight (free) match repeats at the same height on the next drop. A drop (offset) match staggers every second drop by half a repeat, so the offcut from one drop can't start the next — costing about half a repeat of extra waste on every drop. It is the single biggest reason a job comes up short.
| Match type | Typical waste | Why |
|---|---|---|
| Plain / random | ~10% | No pattern to align — every drop is full height and offcuts are reusable. |
| Straight match | 10–15% | Each drop rounds up to a whole repeat so the design lines up across seams. |
| Drop (offset) match | 15–25% | Alternate drops are staggered by half a repeat, so an extra half-repeat is lost per drop. |
Paste, tools and the formulas
Heavier papers need stronger paste. The calculator reads your paper type and recommends a paste family and a number of standard packets — a safer figure than litres, because brand concentrations differ. Here is the maths behind the roll count.
Three formulas turn a room into a roll count.
Drops per roll
⌊ roll length ÷ drop cut length ⌋- Drop cut length = ceiling height + trim allowance.
- For patterns, the cut length rounds up to a whole repeat (plus half a repeat for a drop match).
Rolls to buy
⌈ net drops × (1 + waste) ÷ drops per roll ⌉ − rolls owned- Net drops = gross drops − drops saved by doors and windows.
- Rounded up to whole rolls; rolls you already have are subtracted.
Paste packets
⌈ rolls to buy ÷ rolls per packet ⌉- All-purpose covers ~5 rolls; heavy-duty ~4; ready-mixed ~3.
- A packet count is safer than litres because brand strengths differ.
Worked examples
Two runs through the same 4 m × 5 m room — once plain, once with an offset pattern — show how much the match type moves the roll count.
Same room, two papers. A 4 m × 5 m room is four walls — 4, 5, 4 and 5 m — with a 2.4 m ceiling, a 53 cm × 10 m roll and a 10% waste buffer.
Plain paper
No repeat- Given
- Walls: 4, 5, 4, 5 m; ceiling 2.4 m
- Roll: 53 cm × 10 m, plain (0 repeat)
- Trim 10 cm, waste 10%
- Formula
⌈ drops × 1.10 ÷ drops per roll ⌉- Steps
- Drops: ⌈4/0.53⌉ = 8 and ⌈5/0.53⌉ = 10 → 8 + 10 + 8 + 10 = 36
- Drop cut = 2.4 + 0.1 = 2.5 m → ⌊10 ÷ 2.5⌋ = 4 drops per roll
- 36 × 1.10 = 39.6 → 39.6 ÷ 4 = 9.9 → 10 rolls
- Result
- 10 rolls
Patterned, drop match
50 cm repeat- Given
- Same room and roll as above
- Pattern repeat 50 cm, drop (offset) match
- Formula
drop cut = (repeats + ½) × repeat- Steps
- Still 36 drops to cover the walls
- Cut = (5 + ½) × 0.5 m = 2.75 m → ⌊10 ÷ 2.75⌋ = 3 drops per roll
- 39.6 ÷ 3 = 13.2 → 14 rolls
- Result
- 14 rolls — four more than plain
Common mistakes
Buying short. The number-one cause is ignoring the pattern repeat, especially on a drop match. The waste buffer and the spare roll exist for exactly this.
Mixing batches. Rolls from different print runs (batches) can differ slightly in colour. Buy all your rolls — including the spare — from one batch, and check the batch number on every label.
Forgetting the offcuts don't always fit. Above a door or below a window you need short pieces, but on a patterned paper those offcuts rarely match, so the calculator only deducts openings conservatively.
Frequently asked questions
Short answers to the questions people most often ask about estimating wallpaper, pattern repeats and paste with this calculator.
How many rolls of wallpaper do I need?
Add each wall's width and the ceiling height, choose your roll size and pattern, and the calculator counts the drops, works out the drops per roll, and gives you the whole rolls to buy — including a waste buffer you can adjust.
What is a drop?
A drop is one floor-to-ceiling strip of wallpaper. Decorators count drops rather than area because a roll is divided into whole drops, and that is what makes the roll count accurate.
What is the difference between a straight match and a drop match?
A straight (free) match repeats at the same height on each drop. A drop (offset) match staggers every second drop by half a repeat, so it wastes about half a repeat more per drop — often a roll or two more across a room.
Does the pattern repeat really change how much I buy?
Yes. Each patterned drop is cut to a whole number of repeats so the design lines up, which makes every drop longer than the bare wall height. A bigger repeat means fewer drops per roll and more rolls.
What if my paper is plain?
Enter a pattern repeat of 0. The calculator uses the fast path: every drop is just the wall height plus trim, with no pattern waste, so you typically need fewer rolls.
Does it deduct doors and windows?
Yes, conservatively. Openings reduce the drops in proportion to how much of the wall they cover, but because patterned offcuts above and below an opening rarely match, the deduction stays cautious so you don't end up short.
Which paste should I use?
Light and standard papers hang with all-purpose paste; heavy and vinyl papers need heavy-duty paste; embossed and textured papers suit a ready-mixed paste. The calculator recommends a type and a number of packets from your paper choice.
I already have some rolls — can I account for them?
Yes. Enter the rolls you already have and they are subtracted from the rolls to buy, so you don't over-order when finishing a job or redoing one wall.
Can I use feet and inches?
Yes. Switch between metric and imperial at the top. Room sizes use metres or feet; roll width, pattern repeat and trim use centimetres or inches.
Does it handle US double rolls?
The calculator works in single rolls. US wallpaper is often priced as a double-roll bolt but hung as two single rolls — enter the single-roll width and length from the label, and read the count as single rolls.
Is the calculator private?
Completely. Everything runs in your browser — no account, no upload, and nothing you type leaves your device.