Loan Wallpaper Estimator
Wallpaper rolls lie: the coverage on the label assumes a perfect world with no pattern to match. This estimator subtracts the doors and windows, then applies real-world usable coverage per roll for your pattern repeat.
Counts are in standard US single rolls (about 20.5 in × 33 ft). Most wallpaper is sold as double rolls — the estimator converts for you. All rolls for one room should come from the same dye lot: check the lot number on every label.
How it works
Wall area is the perimeter × ceiling height, minus 21 sq ft per door and 15 per window. The honest part is the divisor: a US single roll holds about 56 sq ft of paper, but after trimming and matching you really get about 30 sq ft of wall per roll for a random match, 27 with a small repeat, and 24 with a large repeat — every strip must start at the same point in the pattern, and the offcut above the door rarely lands where the pattern needs it. Those usable-coverage figures are the wallpaper trade's standard planning numbers.
Formula & worked example
Formula: Net wall = perimeter × ceiling height − 21 sq ft per door − 15 per window. Rolls = net wall ÷ usable coverage per US single roll: 30 sq ft for random match, 27 for a small repeat, 24 for a large repeat. Double rolls = singles ÷ 2, rounded up.
Worked example: A 15 × 12 ft room with 9-ft ceilings, one door and two windows: 486 − 51 = 435 sq ft of wall. Pattern-free paper at 30 usable sq ft per roll takes 15 single rolls (8 doubles); a large repeat at 24 per roll takes 19 singles (10 doubles).
When to use this
- Papering a room and converting 'how many rolls?' from folklore to arithmetic.
- Choosing between a solid and a large-repeat print with the true paper cost visible.
- Ordering for a feature wall only — halve the wall: enter the room length as half the wall's length and the width as 0, and the perimeter math covers exactly that one wall.
- Checking a decorator's roll count before the paper is cut.
How to use it, step by step
- Measure room length, width and ceiling height.
- Pick the pattern repeat honestly — it is printed on the roll label and in the listing.
- Count doors and windows for the subtraction.
- Order the double-roll count shown, all from one dye lot.
- Keep one spare roll unopened until the room is finished and inspected.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Room dimensions | Length, width and ceiling height | Bedrooms 10–15 ft, ceilings 8–9 ft |
| Pattern repeat | How often the design repeats vertically | 0 solids, ≤12 in small, 18–25 in large |
| Doors / windows | Openings subtracted at standard sizes | 1–2 doors, 1–3 windows typical |
Another worked example
A square 10 × 10 ft study with 8-ft ceilings, one door, one window — and a large dramatic repeat: 320 gross − 36 of openings = 284 sq ft, and at only 24 usable sq ft per roll that is 12 single rolls (6 doubles). The same room in a solid grasscloth needs 10 singles — the pattern costs two rolls.
Frequently asked questions
How many rolls do I need for a 15 × 12 ft room?
Perimeter 54 ft × 9 ft ceilings = 486 sq ft; minus a door and two windows (51 sq ft) leaves 435. At 30 sq ft of usable coverage per roll for a pattern-free paper, that is 15 single rolls — 8 double rolls as sold.
Why is usable coverage so much less than the roll size?
A single roll contains ~56 sq ft, but strips are cut to ceiling height plus trim, seams eat width, and pattern matching forces each strip to start mid-roll at the right point in the design. The trade plans on 30/27/24 usable sq ft per roll by repeat size — the defaults here.
Single rolls or double rolls?
Almost all residential wallpaper is priced and sold as double rolls (two singles on one long roll — less waste at the ends). The estimator reports both: 15 singles = 8 doubles, rounding up because partial rolls are not sold.
How much extra does a pattern repeat cost me?
On the default room: no repeat takes 15 rolls, a small repeat 17, a large repeat 19 — the pattern costs about 27% more paper. It is the single most-missed line in wallpaper budgets.
Can I skip subtracting doors and windows?
You can, and many quick calculators do — but on a typical room that over-orders by 2 rolls. The offcuts above doors and windows do get used over closets and behind radiators, which is exactly what the usable-coverage figures already assume.
🖌️ Painting instead of papering?
If the paper loses the argument, the Paint Coverage Calculator gives gallons per room — coats, ceiling and trim included.
How do I paper just one feature wall?
Run the estimator with the room length set to half the feature wall's length and the width to zero — no: simpler, set room length = wall length ÷ 2 and width = 0, doors and windows on that wall only. The perimeter math (2 × (L + W)) then equals your single wall, and the roll count is right.
What does 'dye lot' actually mean for wallpaper?
Paper is printed in runs; colours drift slightly between runs in a way you cannot see roll-to-roll in the store but can see strip-to-strip on the wall. Buy every roll for a room from one lot number, printed on each label.