Wallpaper Calculator

What a standard roll holds

Wallpaper is priced by the roll and sold as a bolt, and those two things are not the same size. The standard American bolt is 20.5 inches wide and 33 feet long. Turn the width into feet and you get 20.5 / 12 = 1.71 feet, so the bolt holds 1.71 x 33 = 56.4 square feet of paper. Many stores call this a double roll and print the price per single roll, which is half a bolt, so a shelf tag that reads $19 per single roll costs $38 for the roll you carry out of the store.

Smaller and larger formats exist. A single roll sold on its own is usually 20.5 inches by 16.5 feet, about 28 square feet. European paper runs 53 centimeters by 10 meters, close enough to the American bolt that the same math works. Grasscloth often comes 36 inches wide and 24 feet long. Peel and stick is usually 20.5 inches by 16.5 feet. Read the two numbers on the wrapper of the roll you plan to buy and type them in, because a guess here throws off everything after it.

One more trap in the size: a bolt is one continuous piece. A listing that says two single rolls means one 33 foot bolt, not two separate 16.5 foot pieces. You cannot splice two short pieces into a full height drop without a seam running across the middle of the wall.

Usable yield: the number the label does not give you

The 56 square feet is what the roll holds, not what reaches the wall. Every drop gets trimmed at the top and bottom, and every drop has to be cut long enough that the pattern lines up with the drop beside it. The Wallcoverings Association estimating guide publishes the yield the trade uses in practice, and it shrinks as the pattern repeat grows.

The right hand column divides the 329 square feet of wall in the worked example below by each yield and rounds up, which takes the count from 6.6 rolls with no repeat to 9.1 rolls at the largest repeat in the chart. The chart is built for normal rooms with walls roughly 8 to 9 feet high. It also assumes you can use short offcuts above doors and windows, which holds in a bedroom and fails in a hallway with six doors.

That is why this calculator runs a second method alongside the square footage one. It counts drops, the vertical strips you hang, and works out how many full drops each roll will give. The drop count is stricter because it will not credit you for offcuts that may not fit anywhere. When the two methods disagree, buy the larger number. The trade chart exists to stop you overbuying, not to stop you running short on a Sunday afternoon.

Count the drops, not just the square footage

A 12 by 14 foot room has 2 x (12 + 14) = 52 feet of wall. With 8 foot ceilings that is 52 x 8 = 416 square feet of wall before any openings are removed. That number is the one people stop at, and it is only half the job.

Now count strips. Two doors take 3 feet of wall each, so the run you paper is 52 - 6 = 46 feet, which is 46 x 12 = 552 inches. Divide by the 20.5 inch width of the roll: 552 / 20.5 = 26.9, so you need 27 drops to get around the room.

Each drop is the wall height plus a trim allowance. Add 4 inches for uneven floors and ceilings, so the minimum cut is 8 feet plus 4 inches, or 8.33 feet. With a 24 inch repeat the cut has to grow to the next full repeat, which takes it to 10 feet. A 33 foot roll gives 33 / 10 = 3.3, so 3 full drops come off each roll and about 3 feet goes in the bin.

27 drops at 3 per roll is 27 / 3 = 9 rolls. Add the spare roll and you buy 10. The same room in a plain paper with no repeat still needs 9 rolls, because the cut only falls from 10 feet to 8.33 feet and 33 / 8.33 = 3.96, which is still 3 drops. The pattern is not what costs you here. The wall height is.

Why pattern repeat changes the count in steps

The repeat does not push the roll count up smoothly. Everything turns on one threshold: a 33 foot roll yields 3 drops only while each cut stays at 11 feet or less, because 33 / 3 = 11. Cross 11 feet and the roll drops to 2 drops, a 50 percent jump in paper for one extra inch of cut.

Read down the middle column and the reason for the odd shape is visible. A 36 inch repeat rounds 8.33 feet up to 9 feet, which fits three times in a roll. A 48 inch repeat rounds the same wall up to 12 feet, which fits twice. A 60 inch repeat rounds to 10 feet and fits three times again. So a big floral with a 48 inch repeat can cost 5 extra rolls in a room where a 60 inch repeat costs none, and no rule of thumb about big patterns catches that.

The table assumes a straight match and an 8 foot ceiling. A drop match, where every other drop shifts down by half a repeat, adds half a repeat to each cut. A 36 inch drop match therefore cuts at 12 feet instead of 9 and needs 14 rolls. The match type is printed next to the repeat on the label, usually as straight, half drop or random.

Doors, windows and the walls you skip

Openings are where most estimates drift. A standard door is 3 by 7 feet, or 21 square feet. A window is usually counted at 12 to 15 square feet: the Wallcoverings Association uses 12 for a 3 by 4 window, while retailer guides often use 15 for a 4 by 4. The gap is 3 square feet per window, which is small in a bedroom and not small in a sunroom.

For the square footage method, subtract doors and windows both. For the drop count, subtract doors only. A door removes a full height strip, so it genuinely removes drops. A window sits in the middle of a strip: you still paper above and below it, and those short pieces come out of offcuts you already paid for. Outlets, switch plates and a bathroom mirror should not be subtracted at all.

In the 12 by 14 room the two doors and three windows take out 2 x 21 + 3 x 15 = 87 square feet, which leaves 329 square feet of wall. That is the number the yield chart divides into, and the number the calculator shows as wall area to cover. If your room has a wide sliding door, count it as two doors. A wall you are leaving bare, behind a bookshelf for instance, should come out of the perimeter entirely, which you can do by entering the length and width of the papered area rather than the room.

Buying the paper: dye lots, spare rolls and cost

Buy every roll in one trip and check the dye lot number on each wrapper. Two rolls from different print runs can be a shade apart, and the difference shows as a band on the wall in daylight. Opened rolls are usually not returnable, and matching a lot six weeks later is often impossible because the pattern has been discontinued.

The spare roll is not superstition. Walls get patched, furniture dents them, and a repair with paper from the same lot disappears. Ten percent extra is the usual allowance, and one spare roll covers that on most rooms. At $38 a roll, 9 rolls cost 9 x 38 = $342 and 10 rolls cost $380. That $38 is cheap next to rehanging a wall because the paper ran out.

Rolls are often sold in pairs, so an odd count gets rounded up at the register. Before you compare two stores, check whether the price is per single roll or per bolt: a store selling single rolls at $22 is more expensive than one selling the same paper in bolts at $40, since 2 x 22 = $44 against $40 for the same 56 square feet. Price per square foot is the only fair comparison, and it is 40 / 56 = 71 cents for the bolt.

Metric rolls, murals and peel and stick

Metric paper at 53 centimeters by 10 meters holds the same 57 square feet, but the width drives the drop count: 53 centimeters is 20.9 inches, so 552 / 20.9 = 26.4, which is 27 drops in this room again. Change the width field and the count follows, which is why the calculator asks for the width in inches rather than offering a single roll size.

Peel and stick is the format that catches people. At 20.5 inches by 16.5 feet, a 10 foot cut leaves one drop per roll and 6.5 feet of waste, so the same room needs 27 short rolls instead of 9 long ones. That is not a worse deal if the short roll costs a third as much, and it is a much worse deal if it costs half as much. Divide the price by the square footage on the label before you decide.

Murals are sold as a fixed panel set rather than by coverage. Measure the wall, order the panel count the listing specifies for that width, and ignore the roll math entirely. A mural that arrives as 6 panels of 24 inches covers 12 feet of wall with no repeat to match, so the only number that matters is wall width divided by panel width, rounded up.