Wallpaper Calculator
Enter your walls, height, roll size and pattern repeat and get the drops you need, full drops per roll and the number of rolls to buy, using a wallpaper maker's method.
Measure each wall corner to corner; include doors and windows.
James Dunlop: 10% for repeats up to 26 cm (about 10 in), 15–20% above that.
Roll size and repeat are on the label. The result updates as you type.
Wallpaper rolls
11 rolls
28 drops needed · 3 full drops per roll · 10 rolls before your 10% allowance
| Drops per wall | 8 + 6 + 8 + 6 |
| Length of each drop (height + trim + repeat) | 121 in |
| Full drops from one roll | 3 |
| Rolls (exact) | 9.33 |
What this page cannot tell you
How the pattern will fall on your walls, or whether rolls come from the same batch. Buy all rolls with the same batch number. Pattern match type (straight or drop) and very uneven walls can use more paper; ask the maker for a figure on unusual rooms.
How to calculate wallpaper rolls
- Measure each wall. Corner to corner; treat doors and windows as wall.
- Measure the height. The height you'll paper.
- Read the label. Roll width, roll length and pattern repeat (0 for random match).
- Add trim and allowance. A trim allowance for top and bottom, and a percentage for waste.
- Read drops and rolls. Drops needed, full drops per roll, and rolls to buy.
10 situations where a wallpaper calculator helps
Ordering a whole batch at once
Rolls from different batches can differ slightly in colour; order enough the first time.
Large pattern repeats
A big repeat wastes paper on every drop; see how many drops a roll really gives.
Accent wall
One wall's drops and rolls.
Comparing papers
Change the repeat and roll size to compare two designs' cost.
US and European rolls
Work in feet and inches or metres and centimetres.
Tall rooms
A taller wall can drop a roll from three drops to two.
Random match papers
Set the repeat to 0 for papers that don't need matching.
Checking a decorator's quote
Compare their roll count with yours.
Ceilings and stairwells
Enter the strip widths and the length of each drop.
Budgeting
Rolls × price per roll before you shop.
Where the method comes from
The method follows the wallpaper and textile maker James Dunlop's guide 'How to calculate wallpaper requirements'. Divide each wall's width by the roll width to get the drops (widths) for that wall, counting part-widths as full widths, because paper shouldn't be turned fully into a corner. Each drop's length is the height plus a trim allowance (their example uses 30 cm, 15 cm top and bottom) plus the pattern repeat; for random or free-match papers no repeat is added. Divide the roll length by the drop length and count only full drops. Rolls = drops needed ÷ drops per roll.
James Dunlop's worked example is reproduced exactly: a 3.5 m wall with 52 cm paper needs 7 drops; at 2.5 m high with a 52 cm repeat each drop is 3.32 m, so a 10 m roll gives 3 full drops. They recommend adding 10% (up to a full roll) for pattern matches up to 26 cm, and 15–20% above that. They also recommend treating walls with doors and windows as full walls.
Limits: pattern match type, very out-of-square walls and unusual rooms can use more. Buy all rolls from the same batch. Everything runs in your browser.
Sources
- James Dunlop Textiles — How to calculate wallpaper requirements — Drops, drop length with trim and repeat, drops per roll, allowance
Frequently asked questions
How do I calculate how many rolls of wallpaper I need?
Count the drops (wall width ÷ roll width, rounded up), work out how many full drops one roll gives (roll length ÷ (height + trim + repeat), rounded down), and divide.
How does pattern repeat affect it?
Each drop has to be cut long enough to match the pattern, so a larger repeat means fewer drops per roll and more rolls.
Should I subtract doors and windows?
James Dunlop recommends treating them as full wall, because cutting around them uses about as much paper.
How much extra should I buy?
James Dunlop suggests 10% for repeats up to 26 cm and 15–20% above that; the page applies the percentage you enter.
How big is a roll of wallpaper?
It varies — read the label. James Dunlop's rolls are 10 m long and 52 or 72 cm wide; US rolls are often given in feet.
What is a random match?
A paper with no pattern to line up, so no repeat is added to each drop. Enter 0 for the repeat.
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