Toolrack

Wallpaper Calculator

Works offlineNothing is uploadedFree, no sign-up
sum of all wall lengths
0 for plain; printed on the label as 'rapport'
door + window widths summed; skip for safety margin
ROLLS TO BUY—
DROPS NEEDED—
DROPS PER ROLL—
CUT LENGTH—

Everything is computed in this tab — nothing is sent anywhere.

How many rolls a room takes, counted the way a decorator strips it: whole drops per roll at your ceiling height — with the pattern repeat rounding every drop up — then drops around the perimeter, then rolls. The repeat is where every hand estimate goes wrong.

Drops, not square metres

Wallpaper is hung in whole drops — full-height strips — so area arithmetic misleads: a roll's 5.3 m² only matter as 'how many whole ceilings fit in 10.05 m'. That integer is brutal: 4 at 2.5 m, but 3 the moment a repeat rounds the cut length past 2.51 m. Every other number follows from it.

The calculator works exactly that chain: cut length (height rounded up to the repeat), drops per roll (roll length ÷ cut length, floored), drops needed (perimeter ÷ roll width, ceiled), rolls (ceiled again). Four operations a decorator does on a cigarette packet — with the rounding in the right places.

Frequently asked questions

What does the pattern repeat actually cost?

One drop per roll, typically. At a 2.5 m ceiling a 10.05 m roll yields four plain drops; with a 0.64 m repeat every drop must be cut at a multiple of 0.64 — 2.56 m — and only three fit. On a standard room that turns nine rolls into twelve, which is exactly the surprise at the till this calculator prevents.

Should I subtract the door and window?

Cautiously. The strips above and below openings come from the offcuts only when the pattern allows; with a large repeat they often do not. Entering opening widths trims the count; leaving them out buys the safety margin decorators actually keep.

Same batch number — why does it matter?

Rolls are dyed in batches and neighbouring batches differ visibly on a wall. Buy all rolls from one batch, and prefer one spare roll from it over a perfect count — a repair or a mistake years later matches only this batch.

Offset (half-drop) patterns — how do I enter them?

Enter the full repeat as the label states it and treat the answer as the safe count: a half-drop match wastes up to half a repeat more per drop than a straight match. If the label says 64/32 offset, use 0.64 here and keep the spare roll.

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