CalcCoverageHow many rolls of wallpaper do I need?
Wallpaper is bought by the roll, but rolls are compared by usable coverage — what is left of the roll after trimming the ends of each strip and matching the pattern. The wall area itself is the familiar perimeter × height, minus the doors and windows you will not paper over (you paper up to them, not across them).
Rolls = (wall area − doors − windows) ÷ usable coverage per roll
Example: a 12 × 12 ft room with 8 ft walls has 384 sq ft of wall. One door (21 sq ft) and two windows (24 sq ft) come out, leaving 339 sq ft — 7 US double rolls at 56 sq ft usable each.
What “usable” means
| Roll type | Roll size | Usable coverage used here |
|---|---|---|
| US double roll | ≈ 67 sq ft on the roll | ≈ 56 sq ft |
| US single roll | ≈ 34 sq ft on the roll | ≈ 28 sq ft |
| European roll | 10.05 × 0.53 m ≈ 57.7 sq ft | ≈ 48 sq ft |
Pattern repeat is the roll-eater: a large repeat (over about 12 in) can push a room up by a roll, because every strip must start at the same point in the pattern. For bold, large-repeat papers, buy one roll beyond the calculator's answer and keep the receipt — returns of a full roll beat an unfinished wall in a discontinued pattern, and dye lots matter in wallpaper just as they do in tile: buy the room in one order.