How many rolls of wallpaper do I need?

Count drops, not square metres. Work out how many widths of paper each wall takes, how many full-height pieces one roll gives, and divide. A 4.2 m × 3.6 m room with walls 2.4 m high takes 8 rolls of 53 cm × 10.05 m plain paper, and 10 rolls of a paper with a 53 cm pattern repeat.

A drop is one full-height length of paper, from the ceiling to the skirting.

The steps

1. Measure each wall’s width and the height from the top of the skirting to the ceiling.
2. Drop length = the height plus about 10 cm, for trimming at the top and the bottom.
3. Allow for the pattern. With a straight match, round the drop up to a whole number of pattern repeats, so that every drop starts at the same point of the pattern. With a half-drop match, add half a repeat as well. A free match, such as a plain, textured or random paper, needs neither.
4. Drops per roll = the roll length ÷ the drop length, rounded down. A part-drop left on the roll is waste.
5. Drops per wall = the wall’s width ÷ the roll’s width, rounded up.
6. Rolls = all the drops ÷ drops per roll, rounded up.

Worked example

A room 4.2 m × 3.6 m, walls 2.4 m high, rolls 53 cm wide and 10.05 m long.

• Drops per wall: 4.2 ÷ 0.53 = 7.9, so 8; 3.6 ÷ 0.53 = 6.8, so 7
• All the drops: 8 + 7 + 8 + 7 = 30
• Drop length for a plain paper: 2.4 + 0.1 = 2.5 m
• Drops per roll: 10.05 ÷ 2.5 = 4.02, so 4
• Rolls: 30 ÷ 4 = 7.5, so 8 rolls, with 2 drops spare

What the pattern does

The same room, with the paper’s repeat and match changed:

Match	Drop length	Drops per roll	Rolls
Free match	2.5 m	4	8
Straight match, 53 cm repeat	2.65 m	3	10
Half-drop match, 53 cm repeat	2.915 m	3	10
Straight match, 64 cm repeat	2.56 m	3	10

A 53 cm repeat turns a 2.5 m drop into five repeats, 2.65 m. Four of those need 10.6 m, more than the roll’s 10.05 m, so each roll gives three drops, and the room needs two more rolls. Most of that extra paper is offcut, and it is the price of a pattern that lines up.

In three of those rows the 10 rolls leave no spare drop. One mis-cut would leave you a roll short, which is why BuildBatch says so on the line.

Doors and windows

BuildBatch does not take them off. The short pieces above a door and below a window are still cut from full drops, so that the pattern carries on across them, and each internal corner wastes a strip. The saving is usually smaller than the area of the opening suggests. Counting whole drops for every wall errs towards a spare drop rather than a wall left unfinished.

For painting, openings are taken off: see doors and windows: what to take off.

The figures come from the label

Everything above depends on four figures printed on the roll’s label: the width, the length, the pattern repeat and the match. Many UK rolls are 53 cm wide and 10.05 m long, and BuildBatch starts with that roll as a labelled example. Wider rolls and other lengths exist, so copy the figures off the paper you are buying.

The label also says how the paper is hung: paste the paper, paste the wall, or ready-pasted. The paste packet says how many rolls it hangs.

Before you buy

• Buy every roll with the same batch number on the label. The colour can differ from one batch to the next, and a matching batch can be hard to find later.
• Check the walls first. Paper shows every bump and crack, so walls are washed, filled and sanded flat. New or very porous plaster is sealed first, as the paste’s instructions say. See preparing walls before painting; the same steps apply.
• Lining paper is hung first on poor or patched walls, and under heavy papers. It is counted the same way as the paper.

The room refresh planner counts the rolls, the paste and the tools from your walls, or from a room you have drawn in the room planner. Choose “Wallpaper them” for the walls, and copy the figures from the label.