Wallpaper Calculator

How to calculate wallpaper: the strip method

Wallpaper goes up in vertical strips, each one roll wide and a little taller than the wall. So the question is how many strips the walls take and how many strips one roll gives. Area comes into it only at the end, as a check.

1. Strips across the walls = total wall width ÷ roll width, rounded up.
2. Strip length = wall height + 4 in for trimming, rounded up to a whole number of pattern repeats.
3. Strips per roll = roll length ÷ strip length, rounded down. The piece left at the end of the roll is too short for a full strip.
4. Rolls = strips ÷ strips per roll, rounded up.

This is the rule in the calculators on the York and Brewster product pages, which run the same script, so we count it as one source, not two.^[1][2] Those calculators leave out the trim. We add the 4 in that the York and Brewster hanging instructions call for, about 2 in at the top and 2 in at the bottom of each strip, and that Graham & Brown also adds to each strip.^[3][4][5]

Example: a 12 × 14 ft room, 8 ft walls, no pattern repeat

1. Wall width: 2 × (12 + 14) = 52 ft = 624 in
2. Strips: 624 ÷ 20.5 = 30.44 → 31 strips
3. Strip length: 96 in + 4 in = 100 in
4. Strips per roll: 396 in (33 ft) ÷ 100 = 3.96 → 3, with 8 ft left on each roll
5. Rolls: 31 ÷ 3 = 10.33 → 11 rolls, plus one spare (see below)

On 8 ft walls the trim allowance is what decides the count: a 33 ft roll gives four 96 in strips but only three 100 in strips, so the 4 in takes this room from 8 rolls to 11 rolls. That is the cautious answer. With openings left in, the paper above doors and below windows is already inside those full strips, so the 8 ft left on each roll is spare; if you are confident trimming close, the no-trim figure is the least you could get by with.

Example: one 12 ft accent wall with a 21 in repeat

1. Strips: 144 ÷ 20.5 = 7.02 → 8 strips. The wall is just over 7 strips wide, so measure it carefully.
2. Strip length: 96 + 4 = 100 in, rounded up to whole 21 in repeats = 105 in (5 repeats)
3. Strips per roll: 396 ÷ 105 = 3.77 → 3
4. Rolls: 8 ÷ 3 = 2.67 → 3 rolls

By area the same wall is 96 sq ft ÷ 56.38 sq ft per roll = 1.70 → 2 rolls, one short.

Why dividing by area comes up short

Area division assumes every square inch of the roll ends up on the wall. It doesn’t: each strip is cut a few inches long, a pattern adds the distance to the next match, and the end of each roll is too short for another strip. For the 12 × 14 ft room, the common methods give:

Sherwin-Williams counts 25 usable square feet in a single roll whatever its width: 416 ÷ 25 = 16.64 → 17 single rolls, sold in pairs as 9.^[6] Brewster says one roll covers about 6 ft of wall with ceilings up to 9 ft, so 52 ÷ 6 = 8.67 → 9.^[7] By the strip count, one roll on 8 ft walls covers 3 × 20.5 in = 5 ft 1 1/2 in of wall with the trim allowance, so those rules run low on this room.

The 4 inch trim allowance and 8 ft walls

A 33 ft roll is 396 in long. Strips exactly 96 in long, with no trim, fit 4 to a roll. Add the 4 in the hanging instructions ask for and the strip is 100 in, so only 3 fit. For the 12 × 14 ft room that is the difference between 8 and 11 rolls. Four strips would use 99 in each, leaving 3 in to trim per strip, 1½ in at each end, with no room for a ceiling that isn’t level or a crooked cut. The calculator follows the instructions. Set the trim to 0 to see the count the York and Brewster calculators give; the results also list it as “With no trim allowance.” For peel-and-stick paper York suggests an inch or two at the top and bottom, so 2 to 4 in in all.^[3]

The same rounding works in your favor above 8 ft. With no repeat, a 20.5 in × 33 ft roll gives 3 strips at any height up to 10 ft 8 in, so 8, 9 and 10 ft walls take the same number of rolls. Hygge & West’s calculator likewise counts 3 strips per roll for its 30 ft rolls on walls 72 to 107 in high.^[8]

Strips per roll by wall height and pattern repeat

Straight match, 20.5 in × 33 ft roll, 4 in trim allowance. Every number comes from the calculator’s strip formula.

Rolls for common room sizes

All four walls, no pattern repeat, 4 in trim, openings not subtracted. Add one spare roll to each figure.

Unless noted, the rolls are 20.5 in × 33 ft. The 27 in × 27 ft roll is shorter but wider, so fewer strips cover the room.

Pattern repeat and match

The pattern repeat is the vertical distance from one point in the design to the place where the same point appears again. It is printed on the label or the product page.^[9] How the strips line up is the match:

• Straight match: the design begins and ends within the roll width, so every strip starts at the same point of the pattern at the ceiling.^[10] Each strip is rounded up to whole repeats, as above.
• Free or random match: strips need no matching and waste the least.^[11] The calculator ignores the repeat.
• Half-drop (offset) match: every other strip is shifted down by half a repeat. Graham & Brown says offset matches take more paper and create more waste, but no maker we checked says how much.^[12] Our assumption: each strip after the first on a roll starts half a repeat further along, so strips per roll = (roll length + half a repeat) ÷ (strip length + half a repeat), rounded down.

Half-drop often costs nothing extra and sometimes a lot. With 20.5 in × 33 ft rolls and 8 ft walls it doesn’t change the 3 strips per roll for any repeat in the table above. But with a 27 in × 27 ft roll and a 21 in repeat, a straight match gets 324 ÷ 105 → 3 strips from a roll, while a half-drop gets (324 + 10.5) ÷ (105 + 10.5) = 2.90 → 2. The 12 × 14 ft room goes from 8 rolls to 12 rolls. If your hanger has a better cutting plan, use their count.

Doors and windows: subtract them or not?

Makers disagree. Thibaut does not recommend deducting doors or windows, Hygge & West suggests including them, and an installer’s site says not to deduct standard-size ones.^[13][14][15] Others do deduct: Brewster takes off one roll for every 4 ordinary doors or windows, Sherwin-Williams takes 20 sq ft for each, and Graham & Brown subtracts the unpapered area.^[16][17][18]

The calculator subtracts nothing unless you enter openings, which is the safer way. For full-height openings such as doors and patio doors it does what the York and Brewster calculators do and removes the whole strips an opening is wide: a 3 ft door is 1 strip of 20.5 in, a 6 ft patio door 3 strips.^[1] Two 3 ft doors bring the 12 × 14 ft room from 31 to 29 strips and from 11 rolls to 10 rolls; one 6 ft patio door gives 28 strips and 10 rolls. Leave windows in: paper still goes above and below them.

Single rolls, double rolls and bolts

Wallpaper in the U.S. is often priced by the single roll but sold in double rolls. Brewster says its paper is priced by the single roll but usually sold only in double rolls, and Thibaut prices by the single roll and packages in double rolls.^[19][13] The common 20.5 in × 33 ft roll is that double roll: York labels it “Double Roll,” Graham & Brown says each roll “equals a double roll” covering up to 56 sq ft, and Brewster calls it a bolt of 56 sq ft.^[20][21][16]

• The calculator counts the rolls you actually take home, at the size you enter. Enter the price of one of those rolls. If the price is per single roll, the 33 ft roll costs twice that.
• Don’t convert with a “single roll = so many square feet” rule. Sources disagree, and the calculator uses the real width and length instead.
• Common sizes: 20.5 in × 33 ft (York, Brewster; Graham & Brown’s is 20.47 in × 32.81 ft), 27 in × 27 ft (York) and 27 in × 30 ft (Hygge & West).^{[20][22][21][23][14]} On October 5, 2026, 626 of the 2,050 products in York’s online catalog came as a 20.5 in × 33 ft double roll and 566 as a 27 in × 27 ft one.^[24]

Buy one more roll, all from one batch

Rolls printed in different runs can differ slightly in color. Graham & Brown says all rolls should be from the same batch, Brewster says to check that the dye lot number matches, and Sherwin-Williams says the same of run numbers.^[25][16][6] A roll bought later to fix a mistake may not match, so buy the spare with the rest. Hygge & West says to order an extra roll if in doubt, and Thibaut recommends up to 20% extra.^[14][13] The calculator shows the count with one spare: 12 rolls for the 12 × 14 ft room. Doing the floor too? The carpet calculator works from the roll width the same way.

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Prepared by the Yard & Build editors. The formulas behind this calculator are checked against hand-worked answers every time the site is built. Maker calculators, roll sizes and hanging instructions checked October 5, 2026.