How the wallpaper calculator works
Wallpaper is bought in rolls but hung in drops, so the calculation goes drop by drop.
- Drop length. Wall height plus a trim allowance of 10 cm. With a patterned paper this is rounded up to a whole number of repeats; with an offset match it is rounded up to the next whole number of repeats plus a half, because neighbouring drops start half a repeat apart.
- Drops per roll. Roll length ÷ drop length, rounded down. A standard 10.05 m roll gives four 2.5 m drops; with a 32 cm repeat on a 2.4 m wall each drop is 2.56 m and the roll gives only three.
- Drops needed. Perimeter ÷ roll width, rounded up.
- Rolls. Drops needed ÷ drops per roll, rounded up, plus the spare rolls.
The spare rolls field adds whole rolls on top, one by default. Keeping one spare roll from the same batch is sensible for later repairs, because batches differ in shade. Set it to 0 if you do not want a spare.
Measuring the room
Measure the perimeter by adding the width of every wall, or enter each wall separately. Include the walls with doors and windows in full unless a wall is almost entirely glass. Measure the height from the top of the skirting to the ceiling or coving line.
Roll sizes
The European standard roll is 0.53 m wide and 10.05 m long. Wide non-woven rolls are 1.06 m wide. American rolls are often 0.52 m wide and 10.06 m long, or sold as double rolls. Enter what is on your label and the calculator will use it.
Imperial units
Switch to imperial to enter feet for heights and perimeters and inches for roll width and pattern repeat. The result is the same within one roll because the calculation is done in metres.
Worked example
A room with 2.4 m walls and a 14 m perimeter, papered with a plain roll of 0.53 × 10.05 m: each drop is 2.5 m including trim, so a roll gives four drops. The perimeter needs 14 ÷ 0.53 = 26.4, so 27 drops, which is 6.75 rolls, so 7 rolls for the drops, plus 1 spare = 8 rolls. Choose a paper with a 32 cm straight-match repeat and each drop becomes 2.56 m, only three drops fit on a roll, and the same 27 drops now need 9 rolls, plus 1 spare = 10. The two extra rolls are the price of the pattern.