Wallpaper Calculator

Wallpaper Calculator counts in drops rather than in area, because that is how wallpaper actually works. A drop is one full-height strip, and it cannot be assembled from two offcuts, so the number of rolls depends on how many whole drops a roll yields rather than on total square metres.

The pattern repeat is the input that changes everything. With a plain paper, a 10 metre roll gives four drops for a 2.4 metre wall with a little over for trimming. With a 64 cm repeat, each drop has to be cut at a whole number of repeats -- 2.56 m rather than 2.4 -- so the same roll gives only three drops, and the room needs a third more paper.

Doors and windows save less than people expect. Each is counted here as about half a drop, because the paper above and below an opening still has to be hung, and the strips either side still have to be full height. Treating a door as a whole drop saved is how rooms end up a roll short.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

• Shows rolls to buy, drops needed, drops per roll, wasted by the repeat and cost together, so you are not running it twice
• A results table you can read across
• Updates as you type, with no button to press and no page reload
• Copy the result in one click
• Free, no sign-up, and it runs entirely in your browser

The wallpaper calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Working out rolls for a feature wall or whole room
• Seeing what a large pattern repeat costs in extra rolls
• Allowing for doors and windows properly
• Costing a wallpapering job