Wallpaper Calculator

How to use this calculator

1. Measure room length, width and wall height.
2. Add up the width of doors and windows — half is deducted, because you still paper above and below.
3. Pick your roll size from the label (US double rolls, UK/EU 10 m rolls or wide rolls).
4. Enter the pattern repeat; large repeats waste more paper per drop.

Method & assumptions

Drops = (Perimeter − ½ openings) ÷ Roll width, rounded up
Drop length = Wall height + Pattern repeat + trim (10 cm)
Drops per roll = Roll length ÷ Drop length, rounded down
Rolls = Drops ÷ Drops per roll, rounded up

Drop

one full-height strip

Pattern repeat

vertical distance before the design repeats

Assumptions & limits

• Straight-match or random patterns treated the same; half-drop matches may need one extra roll.
• Ceilings and feature-wall-only jobs: enter just the walls you are papering (perimeter = sum of their widths).

Rounding: purchase quantities are always rounded up to whole bags, boxes, sheets or bundles. See our methodology.

Worked examples

In depth: wallpaper planning notes

Why wallpaper is counted in drops

Wallpaper is hung in full-height strips called drops, and each roll can only be cut into a whole number of them. That is why area-based estimates often fall short. The drop method works out how many strips fit around the room (wall width ÷ roll width) and how many full strips you can cut from each roll (roll length ÷ (wall height + repeat + trimming allowance)). Rolls equal drops ÷ drops per roll, rounded up.

Openings reduce the number of drops only when they are wide — a standard door saves perhaps one drop, a window often none because you still need pieces above and below. The calculator deducts half of the total opening width you enter — not the area — because short pieces are still needed above doors and above and below windows. That conservative rule matches how many decorators estimate.

Roll sizes, pattern repeat and batches

Roll sizes vary. A standard UK and European roll is 0.53 × 10.05 m; wide rolls of 0.70 m or 1.06 m are common for non-woven papers. In the US, wallpaper is often priced per single roll but sold in double rolls of about 20.5 in × 33 ft. Check the label, and enter the actual width and length.

Pattern repeat is the vertical distance before the design repeats. A large repeat can waste most of a repeat length on every drop, so a 64 cm repeat on a 2.4 m wall can drop a roll from four drops to three. Offset (half-drop) patterns waste more than straight-match ones. The calculator adds the repeat to every drop to stay on the safe side.

Always check that every roll carries the same batch or lot number, because color can vary between print runs. Buy one spare roll for mistakes and future repairs; many retailers accept unopened returns.

Tips & common mistakes

• Check the batch (lot) number on every roll before you start.
• Start papering at a corner or next to a door frame, not in the middle of the main wall.
• Use a plumb line or laser for the first drop on every wall.

Sources

1. Graham & Brown – how to measure for wallpaper — checked 2026-10; verify before launch
2. York Wallcoverings – estimating guide — checked 2026-10; verify before launch
3. British Coatings Federation – wallcoverings — checked 2026-10; verify before launch

Default values (bag yields, coverage rates, densities) are typical figures from manufacturer literature. Always check the label on the product you buy.

Cite or embed this calculator

DIYCalcLab. “Wallpaper Calculator.” Oct 18, 2026. https://diycalclab.com/paint/wallpaper-calculator/

An embeddable version for blogs and contractor sites is planned.