How many rolls of wallpaper do I need?
Wallpaper is not bought by area — it is bought by the roll, and what matters is how many full-height drops you can cut from each one. This wallpaper calculator counts drops the way a decorator does, allows for the trim at top and bottom, and adds the pattern repeat that quietly costs you a roll.
Step 1: count the drops
Measure the perimeter of the room and divide by the roll width. A standard roll is 53cm wide, so a 4m × 3.5m room with a 15m perimeter needs 15 ÷ 0.53 = 28.3, rounded up to 29 drops.
Step 2: work out the drop length
Add about 10cm to the ceiling height for trimming top and bottom. A 2.4m ceiling gives a 2.5m drop. On patterned paper, add one full repeat as well, because every drop has to start at the same point in the design.
Step 3: drops per roll
A roll is 10.05m long, so at 2.5m per drop you get four usable drops — 10m used, 5cm wasted. 29 drops ÷ 4 = 7.25, so the room needs 8 rolls.
What a pattern repeat really costs
The same 4m × 3.5m room with 2.4m ceilings. Only the paper changes.
| Paper | Drop length | Drops per roll | Rolls needed | Wasted per roll |
|---|---|---|---|---|
| Plain, no repeat | 2.50 m | 4 | 8 rolls | 0.05 m |
| 530mm repeat | 3.03 m | 3 | 10 rolls | 0.96 m |
| 640mm repeat | 3.14 m | 3 | 10 rolls | 0.63 m |
A repeat pushes the drop length past a third of the roll, so you lose a whole drop per roll — 25% more rolls for the same room.
Ceiling height matters more than floor area
The cliff edge
Rolls are lost in whole drops, not in centimetres. Raise the ceiling in this room from 2.4m to 3m and the drop length goes from 2.50m to 3.10m — still three drops per roll, but the same 29 drops now need 10 rolls instead of 8, with no more wall area than before.
Doors take width out
A full-height door removes about 90cm from the papered perimeter. One door in this room drops the count from 29 to 27 drops, which saves a roll. Windows usually save nothing, because you still paper above and below them.
Feature walls and part-papered rooms
A single wall
Switch the calculator to one wall and enter its width. A 4m feature wall with 2.4m ceilings needs 8 drops, which is 2 rolls of a plain paper and 3 rolls once a 530mm repeat is added.
Paper above a dado
If you are papering only part of the wall height, enter that height instead of the full ceiling height. More drops fit on a roll, so the count drops sharply — and the paint for the rest is priced with the paint calculator.
Buying and hanging
Batch numbers
Rolls are printed in batches, and colour can shift slightly between them. Buy every roll at once, check the batch number matches, and keep a spare for repairs — a patch from a different batch is visible on a wall even when it looks identical in the hand.
Free match, straight match, offset
A free-match paper has no repeat to line up, so enter zero and every roll gives its maximum drops. Straight and offset matches both need the repeat added; offset patterns also alternate the starting point, which can reclaim some of the waste if you plan the drops carefully.
Preparation
Paper goes on walls that are sound, clean and dry. Fill and sand first, size bare plaster, and expect old vinyl or painted walls to need more preparation than they look. For the wider job, see budgeting a renovation.
Check the roll size on the label
10.05m × 53cm is the UK and European standard, and it is what the calculator assumes. American rolls, grasscloth and many designer papers come in different sizes — read the label and adjust the measurements if yours differ, because a roll that is 10% shorter can cost you a whole extra roll on a tall room.
To convert the same room into a wall area for other materials, use the square meter calculator, or price the whole room with the room renovation cost calculator.