Wallpaper Calculator
Calculate wallpaper rolls from room size, roll width and length, and pattern repeat — with pattern matching, trim allowance and the real waste percentage shown.
Each drop is the wall height plus your trim allowance, rounded up to a whole pattern repeat when the paper has one — that rounding is where most wallpaper waste comes from. Drops per roll = roll length ÷ cut length rounded down; rolls = drops needed ÷ drops per roll rounded up. The waste figure above is calculated, not assumed. Buy every roll from the same batch number and keep a spare for repairs. Estimates only.
What is the Wallpaper Calculator?
The ByteTools Wallpaper Calculator works out how many rolls a room needs. It measures the perimeter, divides it by the roll width to get the number of drops, then works out how many full drops each roll yields once the wall height, your trim allowance and the pattern repeat have been accounted for.
- Pattern repeat handled properly with drop matching
- Works with European and US roll sizes
- Optional deduction of door and window widths
- Trim allowance per drop for top and bottom
- Shows the actual waste percentage, not a guess
- Calculated locally in your browser, nothing uploaded
How to use the Wallpaper Calculator
- 1
Choose metric or imperial and enter the room length, width and wall height.
- 2
Enter the roll width, roll length, pattern repeat and the trim allowance per drop.
- 3
Decide whether to deduct door and window widths, and enter their combined width.
- 4
Tick the spare-roll option if you want one in reserve.
- 5
Read the drops needed, the rolls to buy and the calculated waste percentage.
About the Wallpaper Calculator
The ByteTools Wallpaper Calculator works out how many rolls a room needs. It measures the perimeter, divides it by the roll width to get the number of drops, then works out how many full drops each roll yields once the wall height, your trim allowance and the pattern repeat have been accounted for.
Pattern repeat is where wallpaper waste actually comes from: a drop has to be cut to a whole number of repeats, so a 2.4 m wall with a 64 cm repeat needs a 2.56 m cut. The calculator shows the resulting waste as a calculated percentage rather than a guessed allowance, and can add a spare roll from the same batch.
Both European rolls (53 cm × 10.05 m) and US double rolls (20.5 in × 33 ft) are supported, and everything runs in your browser with nothing uploaded. Results are estimates — measure carefully and buy all rolls from one batch number.
Frequently asked questions
How many rolls of wallpaper do I need?
Divide the perimeter by the roll width to get the number of drops, then divide the roll length by the cut length of one drop to see how many drops each roll yields. A 12 m perimeter room with 2.4 m walls and plain 53 cm × 10.05 m paper needs 23 drops at 4 drops per roll, so 6 rolls.
How does pattern repeat affect how much wallpaper I need?
Each drop has to be cut to a whole number of repeats so the pattern lines up across the seam. A 2.5 m drop with a 64 cm repeat becomes a 2.56 m cut, and a large repeat can easily cost you a whole extra drop per roll. Large repeats mean more rolls.
Should I deduct doors and windows when calculating wallpaper?
Deduct only the full width of large openings such as patio doors or wide windows. Decorators usually paper past normal doors and windows because the offcuts above and below get used elsewhere, and deducting them can leave you short.
How much extra wallpaper should I buy?
Buy one spare roll from the same batch. Batch numbers differ measurably in shade, and a roll bought a year later to patch a damaged strip will rarely match. The spare-roll option in this calculator adds exactly one.
What is the difference between a single roll and a double roll?
US wallpaper is priced per single roll but almost always supplied as a double roll — one bolt of about 20.5 in by 33 ft, roughly 56 sq ft. Always enter the length of the bolt you actually receive, not the single-roll figure it is priced by.
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