Wallpaper Calculator for beginners — start here

If you have never bought wallpaper before, the jargon is the first obstacle, so here it is in plain words. A roll is one packaged length of wallpaper. Coverage is how much wall one roll covers, usually written on the label as square metres per roll, for example 5 square metres per roll. Wall area is the total surface of the walls you plan to paper, measured in square metres, after subtracting doors and windows.

Your first calculation

Take the simplest case first. A room has 30 square metres of wall and each roll covers 5 square metres. Divide: 30 ÷ 5 = 6 rolls. That is the whole calculation. Now try a case that does not divide neatly: 32 square metres with the same rolls gives 32 ÷ 5 = 6.4, and since you cannot buy 0.4 of a roll, the answer is 7 rolls. That round-up is the one rule beginners most often miss, and it is the reason the calculator exists: it applies the rule for you, every time.

Measuring is where most first attempts go wrong, and the mistake is almost always the same: measuring only one wall, or forgetting to subtract a door. Measure every wall, length times height, add them up, then subtract each door and window. A room with 37.8 square metres of wall, a 1.9 square metre door and a 1.5 square metre window has a net area of 34.4 square metres, and at 5 square metres per roll that is 34.4 ÷ 5 = 6.88, which rounds up to 7 rolls.

What to do with the answer

Buy the calculated number, and if you can, one spare roll from the same batch. The spare covers a torn strip during hanging and any repair years later, when the same batch may no longer be in stock. If the pattern is large, the tool's guidance is to add one extra roll beyond the calculated number, because each strip must start at the same point in the pattern and paper is wasted at every join. Start with one room, check the result by hand using the division above, and only then order for the next room.

Frequently asked questions

What is coverage per roll?

How much wall one roll covers, written on the roll label as square metres per roll. A roll covering 5 square metres per roll needs 6 rolls for 30 square metres.

Do I measure the ceiling too?

Only if you plan to paper it. The wall area is the walls only; a papered ceiling is a separate area to add, measured length times width.

Why do I need a spare roll?

For a torn strip while hanging and for later repairs. A spare from the same batch matches in colour, where a later batch may differ slightly.