Wallpaper Calculator

What this calculator does

Wallpaper is sold by the roll, but rooms are measured in walls — so the useful question is always "how many rolls do I actually buy?" This tool bridges the two. You give it your room's length, width, and ceiling height plus how much area one roll covers, and it returns the number of rolls to purchase. It works for feature walls and whole rooms, and it quietly handles the two things people forget: the fabric you lose lining up a repeating pattern, and the wall space taken up by doors and windows.

How the math works

First it finds the wall area: perimeter is 2 × (length + width), and multiplying by height gives the gross square footage. It then subtracts roughly 15 sq ft for every door or window you list. Because a repeating pattern forces you to trim each strip so the design matches the one beside it, only part of each roll is truly usable — so the roll's coverage is reduced by the pattern-repeat waste (about 15% is a safe default). Finally, rolls = wall area ÷ usable-per-roll, rounded up, because you can't buy a partial roll.

Why buy from the same batch

Wallpaper is printed in batches (also called dye lots), and colors can shift slightly between them. Because this tool rounds up and folds in waste, the roll count usually leaves a little spare — order it all at once, from the same batch, so any extra strip you need later still matches perfectly.

How to use it

1. Enter your room's length and width in feet.
2. Enter the wall height, floor to ceiling.
3. Type how many doors and windows are on those walls — each one trims about 15 sq ft.
4. Set the coverage printed on your wallpaper's label (single rolls are often ~28 sq ft, doubles ~56).
5. Adjust the pattern-repeat waste if your paper has a large repeat, then read the rolls-to-buy figure.

FAQ

What coverage should I enter?

Use the square footage on your wallpaper's roll label. A standard American double roll covers about 56 sq ft; a single roll about 28. European rolls list length & width instead, so multiply those.

Why 15% waste?

Matching a repeating pattern means trimming the top of each strip so the design lines up, and that scrap adds up. 15% suits most patterns; raise it to 20–25% for a large repeat, or drop it near 5% for plain paper.

Do doors and windows really matter?

A little. Subtracting ~15 sq ft each keeps you from wildly over-buying on a room full of openings, but the tool still rounds up so you're never short.

How accurate is this?

These are estimates for planning your purchase, not professional advice. Confirm against your paper's roll label and buy from a single batch. Everything runs in your browser — nothing you enter is uploaded.