What's the difference between a US and a European roll?

A US roll covers about 36 sq ft; a European roll is wider and longer, covering about 56 sq ft (≈5.3 m²). Check the label on the roll you're buying — manufacturers print the exact coverage.

Why is the waste factor higher for patterns with a repeat?

Matching a repeating pattern (a "drop match") across seams means cutting off and discarding part of every strip so the pattern lines up. That typically wastes 20-30% of the paper, versus 10-15% for a plain or random-match paper — pick the preset that matches your wallpaper and adjust it if the label gives a specific repeat distance.

Does the roll coverage already account for waste?

No — it's the roll's raw, physical coverage (width × length). We apply the waste factor on top of that, the same way every other calculator on this site does, instead of using a pre-reduced "effective" coverage some sources publish — mixing both would double-count the waste.

How is the net area calculated?

Room perimeter × wall height, minus 21 sq ft per door and 15 sq ft per window — the same net wall area used by the Paint Calculator.

Wallpaper Calculator

Calculate how many rolls of wallpaper you need for a room, US or European roll size.

How we calculate it

Net area = Perimeter × Wall height − Doors × 21 ft² − Windows × 15 ft², Rolls = ceil(Net area / Roll coverage × (1 + Waste factor)).

Understanding your estimate

Buy too few rolls and the wall you're papering stops halfway across, waiting on a supplier that may or may not still stock your exact pattern next week. Buy too many and the extra rolls sit in a closet, because a partial roll of one specific print is hard to return and even harder to reuse on a different job. This calculator exists to get the roll count right in one order, not two.

A bedroom wall, worked out

Take the calculator's own defaults: a 40 ft perimeter, an 8 ft wall height, one door, two windows, US rolls, and the default 12% waste factor for a pattern with no repeat.

Gross wall area: 40 × 8 = 320 ft².
Subtract the openings: one door at 21 ft² and two windows at 15 ft² each, 21 + 30 = 51 ft².
Net area: 320 − 51 = 269 ft².
Add the waste factor and divide by roll coverage: 269 ÷ 36 × 1.12 = 8.37, rounded up to 9 US rolls.
Switch to European rolls (56 ft² each) and the same 269 ft² of wall needs only 6 rolls, same waste factor, same room.

Why the roll count never rounds down

8.37 rolls becomes 9, never 8. This calculator never rounds a roll count down, the same rule every other calculator on this site follows. A wallpaper roll is sold whole, and coming up short mid-room means stopping the job to place a second order before you can finish the wall. One extra roll left over costs you the price of that one roll. Coming up short costs you the whole afternoon.

Why the pattern preset only touches the waste field

Switch the pattern selector from "no repeat" to "repeat" and the waste field jumps from 12% to 25%, but nothing else in the formula changes. That preset is a UI convenience, the same treatment our Tile Calculator gives its laying pattern, straight versus diagonal: the roll-count math itself never receives "repeat" or "no repeat" as an input, only the waste percentage already resolved. Pick a preset and still type your own number afterward, or skip both presets and enter one directly.

Raising the waste factor this way never lowers the roll count you're told to buy. Depending on how close a room already sits to filling a whole extra roll, it can add one roll or leave the count exactly where it was. Either way, it never asks you to buy less.

Why roll coverage doesn't already include the waste

The 36 ft² and 56 ft² roll coverage numbers above are the roll's raw physical size, width times length, not a figure already shrunk to account for pattern matching. The waste factor gets applied on top of that raw coverage in exactly one place in the formula, never folded into the roll size and then applied a second time in the waste field. Counting waste twice that way would quietly push every order higher than it needs to be, and you'd have no way to notice, because an inflated roll size just looks like a normal spec number.

Why roll type has its own field, not a unit toggle

Switching the page to metric doesn't switch the roll type, and that's deliberate. US and European rolls are two different products, not the same roll measured in two systems, the same reasoning that keeps our Roofing Calculator's roof pitch as its own field instead of folding it into the unit toggle. A US roll stays 36 ft² of coverage whether you enter your wall in feet or meters, and picking European rolls stays a separate decision even if you switch back to imperial units afterward.

What this calculator assumes about your walls

This math assumes one wall height for the whole room: perimeter times a single height field, not a wall-by-wall sum. A vaulted section over part of the room, or one accent wall taller than the rest, isn't something this version accounts for; you'd run that section separately and add the rolls. Door and window openings are subtracted at a fixed 21 ft² and 15 ft² each, the same extrapolation our Paint Calculator uses, not the exact size of the door in your house. And like the rest of this site, it doesn't price anything: roll prices swing too much by pattern and retailer for a number fixed here to stay accurate for long.