Wallpaper Calculator
Find how many wallpaper rolls you need, with the pattern repeat and a trim allowance built in.
Calculator
Free, runs entirely in your browser, and your numbers never leave your device. Results are estimates for planning only.
What this calculator does
This wallpaper calculator estimates how many rolls it takes to paper a wall or a whole room. It counts the vertical strips needed to span the wall width, works out how many usable strips you can cut from a single roll once the pattern repeat is matched, and then adds a waste allowance for trimming and the odd mistake.
How to use it
- Add up the width of every wall you are papering and enter that total, plus the wall height.
- Enter the roll's width and length — they are printed on the packaging or the roll's label.
- Enter the pattern repeat; use 0 for a plain paper or a free-match design.
- Set a waste allowance (10–15% is normal) and read the number of rolls to buy.
The formula
Drops = ⌈wall width ÷ roll width⌉. Cut length per drop = ⌈wall height ÷ pattern repeat⌉ × pattern repeat (or just the wall height when there is no repeat). Rolls = ⌈drops ÷ (roll length ÷ cut length)⌉ × (1 + waste %).
Example calculation
A wall 40 ft wide and 9 ft high, papered with 20.5-in-wide, 33-ft-long rolls that have a 19-in pattern repeat, plus a 10% allowance:
- Drops needed: 40 ÷ 1.71 ft ≈ 24 strips
- Cut length per drop: round 9 ft up to a whole repeat ≈ 10.6 ft
- Usable drops per roll: 33 ÷ 10.6 ≈ 3
- Rolls before waste: 24 ÷ 3 = 8
- With 10% allowance: 8 × 1.10 ≈ 9 rolls
Result: About 9 rolls — and keeping one spare from the same batch is wise for repairs.
Buying and planning tips
- Order all your rolls together and check the batch (or lot) number so the color is consistent.
- Keep one full spare roll; matching a new batch later is difficult and the color may drift.
- A larger pattern repeat wastes more paper at the top of each strip, so factor it in for bold designs.
Common mistakes to avoid
- Entering the wall width of just one wall instead of the combined width of every wall.
- Setting the pattern repeat to 0 on a paper that actually has a repeat, which underestimates rolls.
- Skipping the waste allowance, leaving nothing for trimming, mistakes, or future repairs.
Assumptions and limits
- A 10–15% allowance covers trimming and pattern matching; the default is 10%.
- Doors and windows are not deducted, since strips usually run full height around them and the offcuts are small.
- Roll dimensions are whatever you enter — US, European, and designer rolls all differ.
Frequently asked questions
How many rolls of wallpaper do I need?
It depends on the combined wall width, the wall height, your roll's width and length, and the pattern repeat. The calculator counts the full-height strips you need, divides by the usable strips per roll, and adds a waste allowance.
How do I calculate the square footage for wallpaper?
Multiply the combined wall width by the wall height to get the square footage to cover, then divide by the usable area per roll (roll width × length, minus pattern-repeat waste). This calculator does that for you and converts it straight into rolls.
What is a pattern repeat and why does it matter?
The pattern repeat is the vertical distance before the design starts again. With a repeat, each strip must be cut to a whole number of repeats so the pattern lines up, which wastes some paper and can raise the roll count.
How much extra wallpaper should I buy?
A 10% to 15% allowance covers trimming, pattern matching, and mistakes. On top of that, keep at least one spare roll from the same batch so future repairs match.
Do I subtract doors and windows for wallpaper?
Usually not. Strips typically run full height past openings and the offcuts are small, so leaving doors and windows in gives you a useful safety margin instead.
What size is a standard wallpaper roll?
US rolls are commonly about 20.5 in wide and 33 ft long, but European and designer rolls vary widely. Always enter the exact dimensions printed on your roll.
Why does the calculator say a roll is too short?
If a single roll cannot yield even one full-height strip — the wall height plus its pattern repeat — the tool warns you, because you would need to piece strips together. Choose a longer roll instead.
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