Wallpaper calculator with pattern repeat

How many rolls of wallpaper do I need: the strip method

Wallpaper is counted in whole strips (drops, in the UK), not in square feet: divide the roll length by the length of one strip, keep only the whole strips, then divide the strips you need by the strips one roll gives you. This is the method wallpaper sellers such as MEINEWAND use in their guides.

1. Strip length. Wall height plus a trim allowance, rounded up to a whole number of pattern repeats. York suggests about 4 in extra per strip (2 in at the ceiling, 2 in at the baseboard); A.S. Création suggests about 5 cm. With plain paper the repeat is 0 and nothing is rounded.
2. Strips per roll. Roll length ÷ strip length, rounded down: a piece shorter than a strip is no use.
3. Strips per wall. Wall width ÷ roll width, rounded up, wall by wall.
4. Rolls. Total strips ÷ strips per roll, rounded up.

If your walls have different heights, every strip is cut for the tallest one. A little paper is left over, but the count stays safe.

Doors and windows. An opening only saves strips if it is at least one full strip wide. A 3 ft door with a 20.5 in roll saves one strip. Above the door and below a window the wall still needs paper, and those short pieces come out of the offcuts. An opening narrower than a strip saves nothing, because the strip that crosses it is cut full length anyway.

Paste. Wall area minus openings, divided by the coverage of one pack or container, rounded up. Untick the paste box for pre-pasted paper, which you activate with water.

A worked example

In feet and inches (US). The calculator opens with one 12 ft wall, 8 ft high, a double roll of 20.5 in × 33 ft, a 21 in pattern repeat, 4 in trim and paste that covers 330 sq ft per gallon.

• Strip length: 96 + 4 = 100 in; 100 ÷ 21 = 4.76, so 5 repeats: 5 × 21 = 105 in (8.75 ft)
• Strips per double roll: 396 in ÷ 105 = 3.77, so 3
• Strips: 144 in ÷ 20.5 = 7.02, so 8
• Rolls: 8 ÷ 3 = 2.67, so 3 double rolls
• Paste: 12 × 8 = 96 sq ft, one gallon

York lists its rolls as double rolls of 20.5 in × 33 ft, and that is the size the calculator uses in feet. If your paper comes in a different length, enter the length printed on the label.

In metres (UK). A wall 4.00 m wide and 2.70 m high, a 0.53 × 10.05 m roll, a 64 cm repeat and 5 cm trim.

• Drop length: 2.75 m rounded up to 5 repeats = 3.20 m
• Drops per roll: 10.05 ÷ 3.20 = 3.14, so 3
• Drops: 4.00 ÷ 0.53 = 7.55, so 8
• Rolls: 8 ÷ 3 = 2.67, so 3 rolls, and one 25 m² pack of paste for 10.80 m²

The same method gives the MEINEWAND example: a 5 m wall, 2.65 m high, 72 cm repeat, 10 drops of 2.88 m, 3 per roll, 4 rolls.

Wallpaper rolls per room: chart

Double rolls of 20.5 in × 33 ft, 4 in trim, four walls, no doors or windows taken off. The numbers come from the calculator.

Room	8 ft ceiling	9 ft ceiling
10 × 10 ft	8 double rolls	8 double rolls
10 × 12 ft	10 double rolls	10 double rolls
12 × 12 ft	11 double rolls	11 double rolls
12 × 14 ft	12 double rolls	12 double rolls
14 × 16 ft	13 double rolls	13 double rolls

These counts are the same for plain paper and for a 21 in repeat: at 8 and 9 ft a double roll gives 3 strips either way. The repeat starts to cost paper on taller walls. At 10 ft a 24 in repeat makes each strip 144 in long, and a double roll gives only 2.

For UK rooms with 0.53 × 10.05 m rolls and 2.40 m walls, a 3 × 4 m room needs 7 rolls of plain paper but 10 with a 64 cm repeat, because each drop grows from 2.45 m to 2.56 m and a roll gives 3 drops instead of 4. That matches Dunelm's rule of thumb of three drops per roll with a repeat of up to 64 cm.

Roll sizes, paste and a spare roll

In the US the common size is the double roll of 20.5 in × 33 ft, about 56 sq ft. In the UK and Europe most rolls are 0.53 × 10.05 m, about 5.3 m² (Dunelm lists 52 cm wide rolls of the same length). Some papers come in wider rolls or as panels: read the width, length and repeat on the label and enter them. If the label gives a half-drop or offset match, enter the full repeat; the count stays on the safe side.

Ready-mixed paste is sold by the gallon in the US. Sherwin-Williams lists Roman PRO-880 at up to 330 sq ft per gallon, which is where the calculator starts in feet. In metric it starts at 25 m² per pack: Henkel's data sheet gives a 180 g pack of Metylan Vlies 25-29 m² on smooth non-woven paper. Change the coverage in the advanced options to match your product.

A.S. Création recommends keeping a spare roll for later repairs. Buy all the rolls at once and check they share the same batch number, since rolls from different batches can differ slightly in shade.

Common mistakes

• Dividing the wall area by the roll area. For the UK example wall, 10.80 ÷ 5.33 is about 2 rolls, but 3 are needed: offcuts shorter than a drop are wasted.
• Forgetting the pattern repeat. In a 3 × 4 m room with 2.40 m walls, plain paper takes 7 rolls and a 64 cm repeat takes 10.
• Taking every window off the area. A narrow window saves no paper: the strip that crosses it is still cut full length.
• Buying in two goes. The second order can come from a different batch.
• Skipping the trim allowance. Without a little extra at the top and bottom, strips end up short at the ceiling or the baseboard.