Wallpaper Calculator
Wallpaper Calculator: How to Work Out How Much Wallpaper You Need
Working out how much wallpaper you need comes down to four steps: measure each wall, subtract the openings, divide by the roll's coverage, and add an allowance for pattern and waste. Every wallpaper calculator, including a manual one done with a tape measure and a notepad, is doing exactly this underneath — a search for "wallpaper calculator" is really a search for someone else to run these four steps for you, accurately, across every wall in the room. Here's each step spelled out, and where doing it by hand for more than one wall starts costing more time than it saves.
Open the Wallpaper PlannerStep 1: measure every wall separately, not the room as one number
Measure each wall's width and height on its own, rather than adding up a rough room perimeter and one ceiling height — a room is a set of individual walls, and treating it that way catches a sloped section, an alcove, or a taller feature wall that a single blended number would hide.
Step 2: subtract doors and windows above a minimum size
A large window or a doorway removes enough wall to skip a full strip, so subtract its width from that wall's total before working out the strip count — but a small window is often narrower than a single strip anyway, and subtracting it can undercount the strips actually needed either side of it.
Step 3: convert wall width to strips, then strips to rolls
Divide each wall's width by your roll's width to get the number of strips it needs, then divide the wall's height into the roll's length to see how many strips one roll yields — that ratio is what turns a wall's dimensions into an actual roll count, not the wall's area on its own.
Step 4: add a pattern repeat allowance before rounding up
If the paper has a repeat distance, each strip after the first needs extra length trimmed off to keep the design aligned, which lowers how many strips one roll actually yields — build that into step 3 before rounding the final roll count up, not after.
Where doing this by hand starts to cost more time than it saves
Four steps per wall is manageable for one wall; multiplied across a whole room's worth of walls, plus a pattern repeat allowance recalculated each time, it adds up to a lot of arithmetic to get right by hand. A calculator that lets you draw the room once and runs the same four steps against every wall automatically is the point where it stops being worth doing manually.
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See plans & pricingCommon questions
Is a wallpaper calculator actually more accurate than doing the maths myself?
It's the same maths — the advantage isn't a different formula, it's applying it consistently to every wall including the ones a hand calculation is most likely to get wrong, like a sloped section or an alcove.
Does a wallpaper calculator handle pattern repeat and odd-shaped rooms?
A good one does — enter the repeat distance from the roll label and draw the room's actual shape, including sloped walls or alcoves, rather than treating every room as a flat rectangle.
Is there a cost to using a wallpaper calculator?
Getting a roll estimate is free — you'd only pay if you want the exact cutting plan, workbench sheets, and order list on top of the basic roll count.
Do I need to create an account before I can see a result?
No — draw the room and get the roll count first, with no signup required. An account only comes into play if you decide to unlock the full cutting plan afterwards.
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Draw your walls — including sloped sections, alcoves, and single feature walls — and get a free estimate before you buy.
Open the Wallpaper PlannerPlanning a specific room? See how much wallpaper you need →
Quoting this as a job, not a DIY project? Try the contractor estimator →
Ready to draw your own room instead of doing the maths by hand? Open the wallpaper calculator →
Setting up a small home-office feature wall? Home office wallpaper calculator →