How to use it
- Measure the distance round the walls and the wall height, and add up the area of the doors and windows.
- Read the Roll width, the Roll length and the Pattern repeat from the wallpaper label.
- Choose the Pattern match. A half-drop pattern needs more paper than a straight match.
- Read Rolls to buy, then check How the rolls are worked out to see each step.
How the rolls are counted
The walls are covered in strips, one roll width each, so the distance round the room gives the number of strips. Each strip is cut to the height plus a trimming allowance. With a pattern, the strip is then rounded up to whole repeats, so the pattern lines up from one strip to the next.
A roll gives as many full-length strips as fit in its length. The strips are divided by that number, and the result is rounded up to whole rolls.
wall area = perimeter × height − doors and windows
strips = perimeter ÷ roll width (rounded up)
drop = height + trimming, rounded up to whole repeats (a half-drop adds half a repeat first)
strips per roll = roll length ÷ drop (rounded down)
rolls = strips ÷ strips per roll (rounded up)Patterns and matches
A straight match means the pattern is the same at the same height on every strip, so each strip starts at the same point of the pattern and some paper is lost at the top. A half-drop, or offset, match starts every other strip half a repeat lower; it wastes more paper, so it needs an extra half repeat in each drop.
Graham & Brown, a wallpaper maker, describes three match types: free, straight and offset. It advises measuring an extra 10 % for waste. This calculator does not add that 10 %; it counts the trimming and the repeat rounding, so add a spare roll if you want the extra margin.
What this calculator does not include
- Deducting the strips that would be saved by a large window, or the offcuts from the corners of the room.
- Paste, primer, the border or the ceiling strip, and a paper that must be matched across batches.
- Rooms with sloping or curved walls, which need a sample strip cut on the wall.
Worked example: 12 m round the walls, 2.5 m high, 1.6 m² of doors and windows
The wall area is 12.00 × 2.50 − 1.60 = 28.40 m². The walls take 12.00 ÷ 0.53 = 22.64, so 23 strips.
Each strip is 2.50 + 0.10 = 2.60 m. A 10.05 m roll gives 10.05 ÷ 2.60 = 3.87, so 3 strips a roll. Then 23 ÷ 3 = 7.67, so 8 rolls.
| Plain paper | Pattern repeat 64 cm, straight | |
|---|---|---|
| Length of one strip | 2.60 m | 3.20 m |
| Strips from one roll | 3 | 3 |
| Rolls to buy | 8 | 8 |
Frequently asked questions
How many rolls of wallpaper do I need for a room?
Measure the distance round the walls and the height, take off the doors and windows, then follow the steps on this page. A room 12 m round and 2.5 m high with 1.6 m² of openings needs 8 standard rolls.
Why does a pattern need more paper?
Each strip has to start at the same point of the pattern, so the top of the next strip is cut lower and the paper above it is lost. The longer the repeat, the more is lost.
What is the difference between a straight and a half-drop match?
A straight match repeats the pattern at the same height on every strip. A half-drop match starts every other strip half a repeat lower, so it needs an extra half repeat in each drop and usually more rolls.
Should I buy a spare roll?
Yes, if you can. Papers printed in different batches can differ slightly in colour, and a spare roll covers a mistake or a damaged piece. Ask the shop whether they can take back an unopened roll.
Can I use this for a double-width roll?
Yes. Choose 1.06 m as the roll width. Each strip then covers twice the width, so there are half as many strips, but a double-width roll is often cut into two strips and this calculator does not split it.
Does the tool store what I enter?
No. The calculation runs in your browser and nothing you type is sent to us or stored.
Sources
Figures and text last checked on Tuesday, November 10, 2026.