Wallpaper Calculator

Wallpaper math has one trap that catches almost everyone: the pattern repeat. A roll that covers 56 square feet on paper can hang barely 30 once you throw away the waste from matching a big damask across every strip. Under-order and you discover the problem halfway across the wall — and the reorder ships from a different batch, so the second half of your wall ends up a slightly different shade of the same color. This calculator does the math properly. It works out how many full strips fit on one roll (wall height plus the repeat), how many strips your wall needs (wall width divided by roll width), and rounds up to whole rolls. It errs on the side of ordering a little extra. One spare roll from the same batch is the cheapest insurance in home decorating.

How to use this calculator

Measure the wall width at the widest point, wall to wall. Old houses settle — measure at the floor and the ceiling and use the bigger number.
Measure the height from floor to ceiling in two spots and use the taller one. Don't subtract baseboards; you'll trim each strip in place.
Read the roll width and length off the wallpaper label. A standard US double roll is 20.5 inches wide and 33 feet long — a single roll is half that length, and European rolls run slightly different.
Find the pattern repeat on the label, in inches. It's the vertical distance before the pattern starts over — enter 0 for plain papers and random matches.
Enter everything and press Calculate. The math assumes each strip is cut to wall height plus one full repeat so the pattern lines up with its neighbor.
Read the result as whole rolls to buy, then add one spare roll from the same batch number. Batch numbers are printed on the label — same pattern, different batch, visibly different shade.
If the wall is mostly door or window, measure the sections beside and above it separately. Full-width math is deliberately conservative; section math saves a roll on glass-heavy walls.

Formula

Each strip you hang has to be wall height plus one pattern repeat long, so the pattern lines up with the strip beside it. Strips per roll is the roll length divided by that strip length, rounded down — the leftover foot or two is scrap. Strips needed is wall width divided by roll width, rounded up. Rolls to buy is strips needed divided by strips per roll, rounded up. The calculator never rounds in your favor on strips and always rounds up on rolls, which is why its answer is conservative.

Worked example

Say you're papering one 12-foot-wide, 8-foot-tall accent wall with a standard US double roll — 20.5 inches wide, 33 feet long — and the pattern has a 12-inch repeat. Each strip must be the 8-foot wall height plus the 12-inch repeat, so 9 feet per strip. Strips per roll: 33 ÷ 9 = 3.67, rounded down to 3 — that leftover 6 feet is scrap, not a strip. Strips needed: the wall is 144 inches wide, divided by the 20.5-inch roll width, which is 7.02 — rounded up to 8 strips. Rolls: 8 strips ÷ 3 strips per roll = 2.67, rounded up to 3 rolls. Now watch what the repeat costs you. With a plain paper and no repeat, each strip is just 8 feet: 33 ÷ 8 = 4.1, so 4 strips per roll, and 8 ÷ 4 = exactly 2 rolls. That 12-inch repeat added a full roll to the order. This is the mistake that empties wallets — people do the area math, buy 2 rolls, and discover the pattern eats the third roll's worth of paper when they're halfway across the wall.

Measurement tips

Buy every roll at once and check the batch numbers match before you leave the store. Two batches of the "same" paper can differ enough to show a line down the middle of your wall.
Order one spare roll. It's $40–$80 of insurance against a torn strip, a bad cut, and the day five years from now when the dog scratches the corner.
Snap a plumb line for the first strip and trust it, not the corner. Corners are never straight — a strip that's 1/8 inch off at the start is half an inch off by the far wall.
If you're new to this, buy paste-the-wall paper (most non-wovens). You roll paste on the wall and hang dry strips — no booking, no soggy 9-foot strips, far less swearing.
Paste-the-paper the old way only if you book it: fold pasted sides together and wait the full 5–10 minutes the label demands. Hang it early and it shrinks on the wall, opening seams overnight.
Prime with actual wallpaper primer before you hang anything. Roman PRO-977 runs about $25 a gallon, and it's the difference between paper that strips off cleanly later and paper that takes the drywall face with it.
Renters: peel-and-stick from Tempaper or Chasing Paper costs roughly $1–$2 per square foot and repositions without paste. It won't hide textured walls, but it comes off when the lease ends.

Common mistakes

Doing area math — wall square footage divided by roll coverage — and ignoring the repeat. A 24-inch repeat can nearly halve the strips per roll, and area math will leave you a roll short every time.
Measuring one wall and assuming the opposite wall matches. In older homes, "identical" walls differ by inches, and an inch is a strip.
Forgetting that doors and windows still need pattern-matched pieces above and below them. The calculator's full-width approach covers this conservatively — section measuring doesn't, unless you add the pieces back.
Cutting strips exactly to wall height. Pros cut every strip a few inches long and trim top and bottom in place; a strip cut dead-even has nowhere to go when the ceiling waves.
Hanging the first strip against the corner instead of a plumb line. Corners lean, and every strip after follows the lean — by the fourth strip your pattern is visibly drunk.
Mixing single and double rolls of the same pattern. The paper matches but the batch often doesn't, and you'll see the shade change at the seam.

Factors that affect accuracy

Pattern repeat size. This is the big one — a 24-inch repeat on an 8-foot wall turns a 4-strip roll into a 3-strip roll, and the calculator shows you exactly where the money goes.
Match type. Straight match wastes the least; half-drop and offset matches shift every other strip, which can cost you an extra strip per roll on big repeats.
Ceiling height. Nine-foot ceilings are lovely until each roll yields 3 strips instead of 4. Tall walls are where the spare roll earns its keep.
Wall obstacles. Outlets, switches, thermostats — each needs a cutout in a pattern-matched strip, and the cutout piece is scrap.
Roll format. US double rolls (33 ft) and European rolls (about 32.8 ft but often wider at 21 inches) yield different strip counts — always enter the numbers off your actual label.
Wall surface. Thin paper over textured walls shows every bump, and heavy texture can force an extra skim coat of mud before you hang — it doesn't change the roll count, but it changes the weekend.

Please note: material estimates are approximate. Always confirm product coverage with the manufacturer and buy a little extra for cuts, waste and future repairs.

Frequently asked questions

How many rolls of wallpaper do I need for a 12x8 wall?

With standard US double rolls (20.5 in × 33 ft) and no pattern repeat, 2 rolls — each roll yields 4 eight-foot strips and the wall needs 8. Add a 12-inch repeat and it becomes 3 rolls, because each roll only yields 3 nine-foot strips. Enter your exact numbers above; the repeat is what moves the answer.

What is pattern repeat?

It's the vertical distance, in inches, before the wallpaper's pattern starts over — printed on every label. Each strip must be cut one full repeat longer than the wall height so the pattern lines up with its neighbor. Big repeats (18–24 inches) are the reason patterned paper needs so many more rolls than plain.

What's the difference between straight match and half-drop?

Straight match lines up every strip at the same height — least waste. Half-drop shifts every other strip down by half a repeat, which looks great on large florals and geometrics but wastes more paper per roll. Check the label: it tells you which one you're buying, and the calculator's repeat math already accounts for the extra length.

Can I hang wallpaper in a bathroom?

Yes, with conditions. Use vinyl-coated or solid vinyl paper, make sure the exhaust fan actually vents outside, and keep paper away from direct splash zones like inside the shower. Steam is the enemy — in a windowless powder room with a weak fan, paint is the safer call.

What does "double roll" mean?

It's the standard US packaging: one double roll is 20.5 inches wide and 33 feet long, about 56 square feet gross. A single roll is half the length. European brands sell similar but slightly different sizes, so always enter the numbers from your label rather than assuming.

Peel-and-stick or traditional paste wallpaper?

Peel-and-stick is the beginner and renter pick: no paste, repositionable, comes off clean. Traditional pasted paper — especially paste-the-wall non-wovens — hangs flatter, lasts decades, and costs less per square foot at the mid range. The roll math is identical either way; only the hanging technique changes.

Why do all my rolls need the same batch number?

Wallpaper is printed in batches, and dye varies slightly between runs. Two batches of the same pattern can differ just enough to show a visible shade line where they meet on your wall. Buy all rolls — including the spare — at once, and check the batch code on every label before the store bags them.