Wallpaper Calculator
Enter the room's size and wall height, then your wallpaper's match type and pattern repeat. The calculator uses the strip method that professional paperhangers use — counting vertical drops and rounding each to the pattern repeat — so patterned and half-drop papers aren't under-ordered the way a simple area ÷ coverage estimate does. Roll dimensions are under Advanced options.
Your measurements
One side of the room. Perimeter = 2 × (length + width); for a single accent wall, set width to 0 and enter the wall as the length.
The adjacent side of the room. Together with length it sets the perimeter to wrap.
Floor to ceiling. A 4-inch trim allowance is added to every strip automatically.
Random (free) match has no repeat to line up — least waste. Straight match lines the pattern up across strips at the same height. Half-drop offsets every other strip by half a repeat, the most waste.
Wallpaper to buy
8 rolls
29 strips · 3 per roll · Random match
What to buy
- Wallpaper rolls
- 8 rolls(20.5" × 33 ft)
- Wallpaper paste
- 2 tubs(~5 rolls per tub)
Buy every roll from the same batch (dye lot) so the color matches, and grab one extra roll for future repairs — a later batch rarely matches.
Skip if your paper is pre-pasted or peel-and-stick. One tub of premixed adhesive hangs roughly 5 rolls.
Typical installed cost
Installed, materials + labor — a ballpark to sanity-check bids, not a quote. See the cost breakdown.
Estimates only. Verify against your supplier's coverage figures before ordering.
Footprint
Wall elevation to scale
29 strips total · 20.5" wide
The strips
- Perimeter to cover
- 48 ft(2 × (12 + 12))
- Strips needed
- 29 strips(20.5" wide each)
- Cut length per strip
- 8 ft 4 in(incl. 4 in trim)
- Strips per roll
- 3 strips(33 ft roll)
One vertical drop per roll-width across the walls, rounded up. Subtracting openings is optional and off by default.
Wall height + a 4 in trim allowance. A random match has no repeat to line up, so there's no extra.
Plus reusable offcuts: on a random match the leftover is used at the top or bottom of another wall.
Reference
- Gross wall area
- 384 ft²(perimeter × height)
Useful for budgeting only — wallpaper is ordered by the strip, not the square foot, so this won't tell you the roll count for patterned paper.
The formula
Strips = ⌈Perimeter ÷ roll width⌉ · Strip length = (wall height + 4 in trim) rounded up to the pattern repeat · Rolls = strips ÷ strips per roll (rounded up)
Example: A 12 × 12 ft room with 8 ft walls has a 48 ft perimeter — 29 strips of 20.5 in paper. With a random match on 33 ft rolls each 8 ft 4 in strip means about 8 rolls; a 12 in straight-match repeat pushes each strip to 9 ft and the order to 10 rolls.
How it works
- 1Wallpaper hangs in vertical strips, so it's ordered by counting strips — not by dividing wall area by roll coverage, which under-orders patterned paper.
- 2Strips = the wall perimeter divided by the roll width, rounded up. Each strip is one full-height drop.
- 3Strip length = wall height + a 4 in trim allowance, then rounded up to the next full pattern repeat so the design lines up (half-drop matches add half a repeat to alternate strips).
- 4Strips per roll = roll length ÷ strip length, rounded down — partial strips at the end of a roll can't be used on patterned paper.
- 5Rolls = strips needed ÷ strips per roll, rounded up. Buy one batch (dye lot) plus a spare roll for repairs.
Frequently asked questions
How much wallpaper do I need?
Count strips, not square feet. Divide the room's perimeter by the roll width to get the number of vertical strips, work out how many strips you get from one roll (roll length ÷ the strip length, which is your wall height plus trim rounded up to the pattern repeat), then divide. A 12 × 12 ft room with 8 ft walls needs about 8 rolls of standard paper with a random match.
Why not just divide wall area by roll coverage?
Because wallpaper is installed in fixed-length drops that must be pattern-matched. The area method ignores the waste from cutting each strip to a full pattern repeat, so it under-orders patterned and half-drop papers — sometimes badly. The strip method counts the actual drops.
What is pattern repeat and why does it matter?
The pattern repeat is the vertical distance before the design repeats. Each strip has to start at the same point in the pattern, so its cut length is rounded up to a full repeat — a large repeat can waste nearly a repeat's worth of paper per strip, raising the roll count. A random (free) match has no repeat to align, so it wastes the least.
What's the difference between a straight and half-drop match?
A straight match lines the pattern up at the same height across every strip. A half-drop match offsets every other strip by half the repeat, so the design runs diagonally — it looks great but wastes more, because alternate strips need extra length to reach the next match point.
Should I subtract doors and windows?
For normal doors and windows, no — the short offcuts above and below them usually can't be reused on patterned paper, and not deducting keeps you from running short. Only deduct strips for large full-height openings like a wide cased opening or a floor-to-ceiling window wall.