How the wallpaper calculator works
A roll of wallpaper is really a stack of drops waiting to be cut. What limits you is not the paper's total surface but how many full-height strips fit into one roll once each strip has been lengthened to line up the pattern. The offcut left at the end of a roll is usually too short for another drop, which is why a pure area-based estimate almost always comes up one or two rolls short.
Rolls = ⌈ drops ÷ ⌊ roll length ÷ cut length ⌋ ⌉, with drops = ⌈ (wall area − openings) ÷ height ÷ roll width ⌉Wall area is the room perimeter times the height in whole-room mode, or just the one wall's width times the height in single-wall mode. If a roll is shorter than one cut length, as with a 2 m sample roll against a 2.88 m drop, no drop can be cut from it at all: the calculator says so instead of inventing a strip.
The cut length is the wall height plus 10 cm (4 in) for trimming at the ceiling and skirting, then rounded up to a whole number of pattern repeats so that every strip starts at the same point in the design. Doors are counted as about 1.9 m² (21 ft²) and windows as 1.4 m² (15 ft²), converted into an equivalent width of wall.
Worked example
A 4 m × 3.5 m bedroom with 2.5 m walls has a perimeter of 15 m and 37.5 m² of wall. One door and one window remove 3.3 m², leaving 34.2 m², the equivalent of 13.68 m of full-height wall. At 53 cm per strip that is 25.8, so 26 drops. The paper has a 32 cm repeat: 2.5 m + 0.10 m = 2.60 m, rounded up to nine repeats gives a cut length of 2.88 m. A 10.05 m roll yields three such drops (8.64 m) with 1.41 m of waste. 26 drops ÷ 3 per roll = 8.7, so you buy 9 rolls. The same paper in a period room with 3.2 m ceilings tells a different story: 3.30 m rounds up to eleven repeats, a 3.52 m cut, only two drops per roll, 27 drops in total and 14 rolls to buy.
Standard roll sizes
| Roll type | Width × length | Coverage (nominal) |
|---|---|---|
| European standard | 53 cm × 10.05 m | 5.3 m² |
| European wide (non-woven) | 70 cm × 10.05 m | 7.0 m² |
| Extra-wide vinyl | 106 cm × 10.05 m | 10.6 m² |
| US double roll | 20.5 in × 33 ft | about 56 ft² |
| US double roll, wide | 27 in × 27 ft | about 60 ft² |
American papers are often priced per single roll but only sold in double rolls, so check which one the quantity refers to before ordering.
Pattern match and waste
A free or random match (plain, textured, stripes) wastes almost nothing because strips can be hung from any point. A straight match repeats at the same height on every drop. A half-drop match shifts every second strip by half the repeat, so cut drops alternately from two rolls to keep waste down. Large repeats of 50–64 cm can cost a quarter of each roll; the calculator shows this as fewer drops per roll.
Tips before you order
- Check the batch number. Every roll should share the same batch (lot) code; colours shift slightly between print runs.
- Order one spare roll for damaged strips, awkward alcoves and future repairs, especially with a large repeat.
- Measure the tallest point. Floors and ceilings are rarely level; use the maximum height.
- Chimney breasts and alcoves add wall: measure around them rather than across.
- Feature wall only? Switch to single-wall mode and enter the wall's width. A 4 m × 2.5 m wall with no openings is 10 m², 7.5 widths of 53 cm, so 8 drops; at three drops per roll that is 3 rolls.
Frequently asked questions
How many rolls of wallpaper do I need for a 12×12 room?
A 12 × 12 ft room with 8 ft walls has 48 ft of perimeter. With 20.5 in × 33 ft double rolls you cut three 8 ft 4 in drops per roll and need about 25–26 drops after one door and a window, so buy 9 double rolls.
How much does one roll of wallpaper cover?
A European 53 cm × 10.05 m roll covers 5.3 m² on paper, but only about 4.5–5 m² in practice once trim and pattern matching are removed. A US double roll covers about 56 ft² nominal and roughly 45–50 ft² usable.
What does pattern repeat mean on wallpaper?
It is the vertical distance before the design repeats, printed on the label in cm or inches. Each cut drop is rounded up to a whole number of repeats, so a 53 cm or 64 cm repeat can cost one extra roll in four.
Should I subtract doors and windows for wallpaper?
Yes, but only roughly: paper is still needed above doors and above and below windows. Deducting the opening area as this calculator does usually saves one roll in a normal room, never more.
How many extra rolls of wallpaper should I buy?
Buy one extra roll from the same batch. Shops rarely have the same print run months later, and a spare roll lets you replace a damaged strip without a visible colour difference.
Last reviewed: 2026-09-27 · How we calculate