Wallpaper Calculator

How to estimate wallpaper

Almost every wallpaper estimate that goes wrong goes wrong the same way: someone divided wall area by roll area. That method ignores the pattern repeat, and the repeat is the single biggest factor in how many rolls you need.

This calculator counts strips instead, because strips are what you actually hang.

strips needed = wall length ÷ roll width
cut length = wall height + trim, rounded UP to a whole pattern repeat
usable strips per roll = roll length ÷ cut length, rounded DOWN
rolls = strips needed ÷ usable strips per rollRounding the cut length up and the strips per roll down is where the repeat costs you material.

Why area division fails

Take an 8 foot wall and a roll that is 20.5 inches wide by 33 feet long. By area, that roll holds 56 square feet and the room needs however many rolls the arithmetic says.

Now add an 18 inch pattern repeat. Each strip has to be cut at a whole number of repeats so the pattern lines up at every seam. Your wall needs 100 inches including trim. The next whole multiple of 18 above that is 108 inches, so every strip is cut at 9 feet. A 33 foot roll gives you 3 strips of 9 feet with 6 feet left over. That 6 feet is scrap, because it is shorter than a single strip.

So you are using 27 of 33 feet. Eighteen percent of every roll goes in the bin, and no area-based calculation will tell you that.

The repeat is the number to check

Set the repeat to zero and the same room needs fewer rolls. A plain paper or a random match can be cut at exactly the wall height. Set it to 24 inches and the cut jumps to 10 feet, which yields only 3 strips per roll with 3 feet wasted.

Large repeats on tall walls are the worst case. If a paper has a 25 inch repeat and your ceiling is high, check the roll count before you fall in love with the pattern. The same room can need several more rolls than a similar paper with a small repeat.

The repeat is printed on the roll label or the sample book, usually alongside the match type. A straight match lines up horizontally across the seam. A drop match offsets each strip by half a repeat, which is more forgiving of waste but harder to hang.

Roll dimensions vary, so read yours

There is no universal roll. American wallpaper is commonly sold as a double roll around 33 feet long and about 20.5 inches wide. European rolls are usually narrower and shorter. Both numbers vary between manufacturers.

This calculator defaults to the common American figures and puts all three fields in front of you. A default that is wrong for your roll gives an answer that is confidently wrong. Read the label and type in what it says.

Doors and windows barely help

This is where wallpaper differs from paint. With paint, an opening removes its full area from the job. With wallpaper, you still hang paper above and below a window. The offcuts usually cannot be reused, because the pattern will not line up where you need it.

So this calculator credits each opening with saving about half a strip rather than its full area. That is deliberately conservative. Being one roll over is a minor annoyance; being one roll short of a discontinued batch is a real problem.

Buy the whole job in one batch

Wallpaper is printed in production runs and the color varies between them. Two rolls of the same pattern from different batches can look obviously different on the same wall, particularly in flat light.

Every roll carries a batch or run number. Check them all match when the order arrives, before you start hanging, and order the spare roll at the same time.

Where the repeat actually bites

The repeat costs you a roll only when it pushes the cut length past a strips-per-roll boundary. That is worth understanding, because it means the damage comes in jumps.

Take a 7 foot basement wall and a 33 foot roll. You need 88 inches including trim, which is 7.33 feet, so a plain paper yields 4 strips per roll. Add a small 9 inch repeat and the cut goes to 90 inches, 7.5 feet, still 4 strips. Nothing lost. But a 25 inch repeat forces the cut up to 100 inches, 8.33 feet, and now only 3 strips come off the roll. Same wall, same room, and your roll count just jumped by a third.

On a standard 8 foot wall with a 33 foot roll, most repeats still give 3 strips per roll. The repeat only costs you scrap. Change the height or the roll length and the boundary moves. That is why the calculator shows usable strips per roll as its own line. That integer, not the area, is what your bill is made of.

A quick cost check

A 12 by 14 room with 8 foot walls has 52 feet of wall. At 20.5 inches wide that is 30.4 strips, less about 1.5 for a door and two windows, so 29. At 3 usable strips per roll that is 9.67, so 10 rolls.

At $60 a roll that is $600, and buying one roll short of a discontinued batch is the failure mode worth $60 to avoid.

Common estimating mistakes

• Dividing wall area by roll area. The method that ignores the repeat entirely.
• Using a generic roll size. Widths and lengths vary by manufacturer and region.
• Subtracting openings at full area. You still paper around them and the offcuts rarely match.
• Ordering rolls in separate batches. Visible color difference, and no fix once it is on the wall.
• Forgetting trim allowance. You hang long and trim both ends, and ceilings are rarely level.

When to hand it over

Wallpaper is more about patience than skill, but a few situations are hard. One is a high stairwell wall, where you work off a ladder with a wet 9 foot strip. Ceilings are another. So is any large repeat on a wall with a lot of corners, since out-of-plumb corners force pattern breaks that need planning.

Check one thing first. If you are stripping old paper in a home built before 1978, the wall underneath may have lead paint. Steaming or scraping it can release dust. Test before you start.