Wallpaper Calculator

Wallpaper is sold by the roll but hung in full-height strips, which is why this wallpaper calculator counts strips instead of square feet. A 20.5 in × 33 ft roll holds 56.4 sq ft, yet on an 8 ft wall it yields only three 100 in strips (96 in of wall plus 4 in of trim), and a pattern repeat adds offcuts. For the bedroom above, 374 sq ft ÷ 56.4 suggests 7 rolls; the strip count is 10 rolls, and a later reorder may not match the shade.

Still deciding between paper and paint? The Paint Calculator handles the same walls in gallons, and the Square Footage Calculator covers irregular floor plans.

The strip method formulas

The calculator follows a paperhanger's procedure. The brackets ⌈ ⌉ mean round up and ⌊ ⌋ mean round down:

Alignment is the paper lost at the start of a roll before the design lines up: up to one repeat for a straight match, half a repeat for a half-drop. The +1 counts the last strip, which needs no offcut after it. The common shortcut, roll length ÷ (wall height + repeat), usually agrees but ignores the trim, so it can be off by a strip per roll either way.

Worked example 1: a 12 × 14 ft bedroom

The calculator's defaults: 8 ft ceilings, one 32 × 80 in door, two 36 × 48 in windows, 20.5 in × 33 ft rolls, a 21 in straight match, 4 in of trim and a 10% spare.

1. Strips: 2 × (12 + 14) = 52 ft = 624 in, and 624 ÷ 20.5 = 30.44, so 31 strips.
2. Openings: the door equals 32 × 80 ÷ 96 = 26.7 in of full-height wall and the windows 36 in, together 3.06 strip widths. Three strips come off, leaving 28.
3. Cut length: 96 + 4 = 100 in, which the 21 in repeat stretches to 105 in of roll (five repeats).
4. Strips per roll: (396 − 21 − 100) ÷ 105 = 2.62, rounded down to 2, plus 1 = 3.
5. Rolls: 28 ÷ 3 = 9.33, so 10 rolls. With the spare, 28 × 1.1 = 30.8 rounds up to 31 strips and 11 rolls.

The 28 strips hung add up to 398.6 sq ft, or 1.6 gallons of paste at 250 sq ft per gallon, so you buy 2. At the example prices of $60 a roll and $25 a gallon the total is $710, for 620 sq ft of paper covering 374 sq ft of wall. The repeat costs nothing here: a random-match paper also gets three strips per roll.

Worked example 2: a 13 ft accent wall under a 10 ft ceiling

Choose Specific walls, enter one 13 ft wall, set the height to 10 ft and the openings to zero. The wall needs 156 ÷ 20.5 = 7.61, so 8 strips. Each 124 in cut uses 126 in of roll with a 21 in repeat, so a roll fits (396 − 21 − 124) ÷ 126 = 1.99, rounded down to 1, plus 1 = 2 strips. That makes 4 rolls, or 5 with the spare, where an area estimate for the 130 sq ft wall says 3.

At 8 ft the same wall yields three strips per roll and needs 3 rolls even with the spare. At 10 ft a random-match paper also yields three (3 × 124 = 372 in), while a 21 in half-drop needs 136.5 in per strip and stays at two.

Rolls needed for common room sizes

Rectangular rooms, no openings deducted, no spare, 20.5 in × 33 ft rolls and 4 in of trim. At 8 and 9 ft a random-match paper and a 21 in repeat need the same count; at 10 ft the repeat costs a strip per roll.

The area-only column is 2 to 4 rolls short in every row. A standard door and two windows usually take one roll off the strip counts, and a 10% spare adds about one back.

Straight match, half-drop and what the repeat costs

A straight match repeats the same motif along the ceiling line. A half-drop shifts every other strip down half a repeat, so installers often cut from two rolls at once to keep the strips in order. A random match has nothing to line up. These are the strips per 33 ft roll with a 4 in trim allowance; the 25.2 in column equals a 64 cm repeat. The half-drop columns assume each roll is cut in order, alternating the two strip types, which is how the calculator counts them.

Neither match is always cheaper. On a 7 ft wall a 21 in half-drop advances 94.5 in per strip and gets four, while a straight match needs 105 in and gets three; at 9.5 ft it flips (136.5 in and two against 126 in and three). Where the half-drop step is the longer one, cutting the odd-numbered strips from one roll and the even-numbered strips from another lets each roll advance by the straight-match step instead, so the calculator's half-drop count is the cautious one. A 9 ft wall gets three strips with a 21 in straight repeat but two with a 22 in one, so use the exact repeat.

Doors, windows and the whole-strip rule

Doors need paper above them and windows above and below, and those short pieces are cut and matched like full strips. The calculator converts each opening into full-height-equivalent width (width × height ÷ wall height), adds them up and deducts only whole strip widths: on an 8 ft wall a 32 × 80 in door (26.7 in) saves one strip, a 36 × 48 in window (18 in) none on its own, and a 72 in patio door (60 in) two.

How to measure and use this calculator

1. Pick the mode: Whole room (length and width, walls papered continuously) or Specific walls (up to eight widths, each rounded to whole strips).
2. Measure the height from floor to ceiling in three places and use the largest figure. 8 ft 6 in is 8.5.
3. Enter doors and windows in inches, or leave them at zero.
4. Copy the label: roll width, length, repeat and match, or pick a preset. For metric labels divide centimeters by 2.54 and meters by 0.3048.
5. Set trim and spare. 4 in per strip, 2 in at each end, is a common allowance, and 10% covers mistakes and a later repair.
6. Add paste and prices to see the material cost next to the roll count.

Roll sizes, paste and price

U.S. wallpaper usually comes in double rolls about 20.5 in × 33 ft (roughly 56 sq ft), often priced per single roll of half that length, so enter the price of the roll as sold. European rolls are typically 0.53 m × 10.05 m, about 20.9 in × 33 ft, and some papers come 27 in × 27 ft. Length beats area: a 27 ft roll holds 60.75 sq ft but fits only two 105 in strips on an 8 ft wall with a 21 in repeat, so example 1 would need 11 such rolls (13 with the spare) instead of 10 (11).

Paste is figured on the strips actually hung (strips × cut length × roll width) divided by the coverage you enter. The default of 250 sq ft per gallon sits below the up to 330 sq ft per gallon listed for one widely sold clear premixed adhesive, because porous walls absorb more. Prepasted papers need only water.

Who this calculator is for

• Homeowners and renters ordering a room or accent wall in one batch.
• Painters and paperhangers quoting rolls and paste.
• Designers comparing papers with different repeats or roll sizes.
• Peel-and-stick users: the strip math is the same, so choose Prepasted and enter the roll size from the box.

Key terms

• Strip (drop): one full-height length of paper.
• Pattern repeat: the vertical distance before the design repeats, printed on the label.
• Straight, half-drop and random match: the motif sits level on every strip, drops half a repeat on every other strip, or needs no alignment at all.
• Double roll: one continuous roll, usually 20.5 in × 33 ft.
• Batch (run) number: the print-run code on the label; rolls from one run share the same shade.

What changes the roll count, and how to save paper

• Height against roll length. A 33 ft roll gives three strips up to about 9 ft, and a repeat often cuts that to two at 10 ft.
• Trim allowance. With a random-match paper on 8 ft walls, 3 in of trim (99 in strips) fits four strips per roll instead of three, taking the example bedroom without openings from 11 rolls to 8. Try this only with a straight ceiling line.
• Repeat, roll size, openings and spare change the count as described above.

Buy all rolls with one batch number and keep the labels, number the strips as you cut them (especially for a half-drop), and cut the short pieces over doors from roll ends. In a home built before 1978, test old paint for lead before sanding or scraping during wall preparation, following EPA's lead-safe guidance.

Limitations

• The roll label's width, length and repeat are taken as exact.
• Ceilings, stairwells, slopes and dormers are not modeled.
• Openings and pattern alignment are handled conservatively; roll ends or a lucky pattern start can save a little more.
• Out-of-plumb walls and corners that need extra overlap add waste that the spare has to absorb.

Related calculators

Use the Paint Calculator for trim and the walls you are not papering, the Drywall Calculator for repairs before you paper, the Square Footage Calculator for irregular rooms, and the Flooring Calculator or Tile Calculator if the floor is part of the project.

Sources

The roll count is geometry applied to your measurements, so no outside data enters it. All example and table figures come from the calculator's own code, and the strips-per-roll formula was checked against a simulation of every possible pattern starting point.

• Roman PRO-880 Ultra Clear Strippable Wallcovering Adhesive, product information: "Covers up to 330 square feet per gallon."
• U.S. Environmental Protection Agency, The Lead-Safe Certified Guide to Renovate Right: lead-safe work practices for homes built before 1978.
• Roll dimensions: the presets are common label formats; use the label on your own rolls.