Wallpaper Calculator

Wallpaper Calculator works out how many rolls a job takes — properly, from the pattern repeat, rather than by adding a flat ten percent to an area. Enter the wall, the repeat printed on the label and the roll size, and read the rolls to buy straight away. It works completely offline and nothing you enter ever leaves your phone.

HOW IT WORKS
Wallpaper is not sold by the square metre. It comes in a fixed-length roll that you cut into vertical drops, so the only figure that matters is how many whole drops come off one roll:

1. The raw drop is the wall height plus a trim allowance for the ceiling line and the skirting.

2. On a patterned paper every drop has to start at the same point in the design as its neighbour, so the cut length is rounded UP to a whole number of pattern repeats. On a half-drop (offset) match, alternate drops start half a repeat further along the roll, so every drop has to carry that extra half repeat and the cut grows again. On a free or random match there is nothing to line up and the cut is simply the raw drop.

3. Drops per roll is the roll length divided by that cut length, rounded DOWN — whole drops only. Whatever is left at the end of the roll is too short to hang.

4. Drops needed is the wall run divided by the roll width, rounded up. Rolls to buy is drops needed divided by drops per roll, rounded up.

Because of step 3 the waste is lumpy, not a percentage. A 2.4 m wall with a 53 cm repeat needs a 2.65 m cut, so only three drops fit a 10.05 m European roll and 2.10 m of every roll is scrap before you count the trim. The same wall on a free match cuts at 2.50 m, four drops fit, and almost nothing is lost. The app shows you the waste the geometry actually produces.

WHAT YOU CAN DO
- Switch between a feature wall and a whole room, and read the rolls to buy instantly
- Choose free, straight or half-drop match and watch the cut length and the roll count move
- Enter any pattern repeat and trim allowance from the label
- Use the European standard roll of 10.05 m by 53 cm, an American double roll, or type your own
- Deduct large openings such as doors and patio sliders, which save whole drops, while ordinary windows correctly save none
- See the paste you need for paste-the-wall or paste-the-paper hanging
- Open Details for a step-by-step breakdown, a waste breakdown, the same job priced on all three match types, and a roll-format reference table
- Learn the geometry behind the numbers in plain language

BUILT FOR CLARITY
A deep indigo, drop-and-repeat design puts the roll count first with the supporting figures beside it. Light and dark themes, a tiny download, no clutter and no account required.

AN ESTIMATE, NOT A DECORATOR'S QUOTE
This is a simplified educational tool. Roll lengths, widths, repeats and match types vary by design and by maker, so always read them off the label. Chimney breasts, alcoves, arches, stairwells and bay windows all change the drop count, and offcuts above and below smaller windows rarely match anywhere else on a patterned paper. Order every roll from the same batch or dye lot, because a second batch of the same design can differ enough to show at the seam. Confirm the final quantity with your supplier or decorator before ordering. This app is for general information and education only and is not professional decorating advice.

PRIVACY
The app collects no personal data and works fully offline. Ads are served by Google AdMob, which may use an advertising identifier as described in Google's policies.

Download Wallpaper Calculator and find out what that beautiful big repeat is really going to cost you in rolls.