How many rolls of wallpaper do I need?

Dividing the wall area by the area of a roll gives the wrong answer for wallpaper. Each roll is cut into full-height strips, called drops, and the leftover at the end of a roll is often too short to use. The reliable method counts drops.

The drop method

1. Measure the perimeter of the room: add the lengths of all walls you will paper.
2. Drops needed = perimeter ÷ roll width, rounded up.
3. Drop length = wall height + pattern repeat + trimming allowance (about 10 cm).
4. Drops per roll = roll length ÷ drop length, rounded down.
5. Rolls = drops needed ÷ drops per roll, rounded up.

Worked example

A room 4 m by 3.5 m has a perimeter of 15 m. Walls are 2.4 m high. A standard European roll is 10.05 m long and 53 cm wide.

• Drops needed: 15 ÷ 0.53 = 28.3, so 29 drops.
• Plain paper, no pattern repeat: drop length 2.4 + 0.1 = 2.5 m, so 4 drops per roll.
• Rolls: 29 ÷ 4 = 7.25, so 8 rolls.

With a 53 cm pattern repeat, each drop needs 3.03 m, only 3 fit on a roll, and you need 10 rolls. Pattern repeat changes the answer more than anything else.

Let the calculator do it

The Paint and Wallpaper Calculator has a wallpaper mode. Enter the room size, wall height, roll width and length, pattern repeat and trim, and it shows the drop length, drops per roll, drops needed and rolls to buy, in metric or US and imperial units.

Doors and windows

Decorators usually count the full perimeter and do not subtract doors and windows. The short pieces needed above and below them still use up drops, and the spare paper covers mistakes. For a room with a very large window or patio door, you can subtract it, but keep a margin.

Read the label

• Roll size: European rolls are commonly 10.05 m × 53 cm. American rolls vary and are often sold as double rolls. Use the dimensions on the label.
• Pattern repeat and match: a straight match lines up across the same height; an offset or drop match shifts by half a repeat, which can waste more.
• Batch number: colours vary slightly between print runs. Buy all rolls from the same batch, and buy one extra, because a matching roll may not be available later.

Feature walls

For a single wall, the perimeter is just that wall's width. A 3.6 m wall needs 7 drops of 53 cm paper. With 4 drops per roll, that is 2 rolls; with a large pattern repeat, possibly 3.

For painting the other walls, see how much paint you need. For converting between feet and metres, use the Length Converter.