Wallpaper Calculator
Paper is hung in drops, so this page counts drops. It cuts each drop to your wall height plus a trim allowance, rounds that up to a whole pattern repeat on a patterned paper, and then works out how many whole drops come off one roll, which is a floor and not a division: the piece left on the end of a roll is not a drop. Wall run over roll width, rounded up, gives the drops you need, and those two numbers give the rolls. The trim allowance and the roll size are fields with stated starting values rather than fixed assumptions, and your doors and windows come off the run only when you say so.
Type the wall run and the height below. The cut length, the drops a roll yields and the rolls to buy appear here.
40 ft of wall 8 ft high, papered from a 20.5 in by 33 ft roll with a 19 in repeat, is 24 drops cut at 9 ft 6 in, three drops a roll, eight rolls.
- Drops
- 0
- Per roll
- 0
- Rolls
- 0
- Cut
- 0
- Spare drops
- 0
- Off each drop
- 0
- Left on a roll
- 0
The wall
The run is every wall you are papering, added together. Feet and inches are read as written, so 8' 6" is fine, and so is 8.5.
Measured a room rather than a wall? Put its two sides in and take the run around it.
The roll
Both figures are printed on the roll. These buttons set the sizes rolls are commonly sold in, and the size on your roll wins over any of them.
The pattern
Every drop starts at the same point in the pattern.
The trim allowance is the spare on each drop for trimming at the ceiling and the skirting, top and bottom together. It opens on 4 in, which is the usual allowance, and it is a field rather than a fixed assumption: change it and the length each drop needs changes with it, before any repeat is rounded up.
Doors and windows
Nothing comes off the run: the drops hang past the opening and are cut round it.
Worked examples
Each one runs through the same function as your own numbers, so a worked example cannot drift from the calculator above it. Load one to see it in the fields.
Every measurement stays in this browser: nothing is sent anywhere and there is no account. The roll buttons are the sizes paper is commonly sold in, 20.5 in and 53 cm among them, and not a price list.
Common questions
- How many rolls of wallpaper do I need?
- Take the worked example on the page: 40 ft of wall 8 ft high, papered from a 20.5 in by 33 ft roll with a 19 in straight repeat. Each drop needs the 8 ft of wall plus the 4 in trim allowance, which is 8 ft 4 in, and rounding that up to six whole repeats of 19 in makes the cut 9 ft 6 in. A 33 ft roll gives three of those and the 4 ft 6 in left on the end is not a fourth. The 40 ft of wall divided by the 20.5 in roll width, rounded up, is 24 drops. 24 drops at three a roll is 8 rolls.
- What does the pattern repeat do to the number of rolls?
- It lengthens every drop, because each one has to start at the same point in the design. On that same wall the repeat turns an 8 ft 4 in drop into a 9 ft 6 in cut, so 1 ft 2 in is cut off each of the 24 drops. The effect is stepped rather than smooth: raise the ceiling from 8 ft to 9 ft and the cut is still 9 ft 6 in, because 9 ft 4 in still fits inside the same six repeats, and the order is still 8 rolls. A paper with no repeat, or a free match, is cut to the wall itself and nothing is rounded.
- What is a half-drop match, and what does it cost?
- On a half-drop, or offset, match every other drop starts half a repeat further along the roll, so the page adds that half repeat to each cut. The 9 ft 6 in cut becomes 10 ft 3.5 in. On the example wall a 33 ft roll still yields three drops, so the order is still 8 rolls, but the margin is thinner: the length left on the end of each roll falls from 4 ft 6 in to 2 ft 1.5 in. A hanger who cuts drops in pairs can win some of that back, which is why the allowance is shown as its own figure rather than hidden in the total.
- Should I take the doors and windows off?
- That is your call, and nothing comes off unless you make it. The page opens on papering over every opening, because drops still run past a window and the offcut is rarely another drop. Set it to floor-to-ceiling only and openings at least 80 percent of the wall height come off while shorter ones stay in: a 3 ft door on the example wall takes the 24 drops to 22, which is still 8 rolls with two drops spare. Set it to every opening and a 3 ft door with two 3 ft windows takes it to 19 drops and 7 rolls.
- Why not just divide the wall area by the area printed on the roll?
- Because that spends the offcut you cannot use. The 24 drops in the example are 228 ft of paper and a roll is 33 ft, so an area or length calculation says 6.9 and buys seven rolls. Hung in drops, a roll gives three 9 ft 6 in drops and 24 drops need eight rolls. The same floor works the other way too: with no repeat and a 7 ft 9 in wall the cut falls to 8 ft 1 in, four drops come off each roll, and the same 24 drops need only 6 rolls. The roll count moves in steps because whole drops do.
- Does it work in metres, and with European rolls?
- Yes, and each measurement keeps its own unit, because a roll is quoted 53 cm wide by 10.05 m long and a wall is measured in metres. The metric worked example is a 4 by 3 m room, so 14 m of wall, 2.4 m high with a 10 cm trim allowance and a 60 cm repeat: the 2.5 m a drop needs rounds up to five whole repeats, which is a 3 m cut, a 10.05 m roll yields three of those, and the 27 drops come to 9 rolls. Feet and inches are read as written as well, so 8' 6" and 8.5 both work.
- What is the trim allowance, and can I change it?
- It is the spare added to each drop for trimming at the ceiling and the skirting, top and bottom together, and it opens at 4 in because that is the usual allowance. It is a field, not a fixed assumption: type 0 and each drop is cut to the bare wall height, and raise it and every drop needs that much more before any repeat is rounded up. On a patterned paper the change often disappears into the same whole repeat, and on a plain one it lands on every cut, which is why the working spells out both lengths. On a tight roll it can be the difference between three drops off a roll and two.
- Is anything uploaded?
- No. Every measurement is read and multiplied in your browser, nothing is sent anywhere and there is no account. Your wall, roll, repeat, trim allowance and openings are remembered in your own browser storage so the page reopens where you left it, and clearing your browser data clears them. The Copy button puts the whole order on your clipboard as plain text, wall and roll included, so it can go straight into a note or an email.
Exact arithmetic on the dimensions you enter: each drop is rounded up to a whole pattern repeat, which is where most of the extra goes. Openings are only deducted if you say so, and it gives no advice on paste, lining or wall condition.