Wallpaper is measured in drops and rolls, not square feet — and thinking in drops is what separates an accurate order from a hopeful one. This guide explains the drop method professionals use to sanity-check any roll estimate.
Think in drops
A drop is one full-height strip cut from the roll. Measure the wall width and divide by the usable width of the paper (usually about 20.5 inches for a standard roll after trimming): that is your drop count for the wall. Then measure the wall height and add at least 4 inches for trimming top and bottom — that is your drop length. Drops per roll = roll length divided by drop length, always rounded down.
Pattern repeat changes everything
Every patterned paper repeats its design at a fixed interval printed on the label — anything from 10 to 25 inches. Each new drop must start at the point in the pattern that matches its neighbour, so on average half a repeat is wasted per drop. Large repeats are the reason a roll that covers 56 sq ft on paper may only put 25 sq ft on your wall.
Work around the room in order
Start at the least visible corner or behind a door, and plan the last join to land there too — pattern drift accumulates and the final mismatch should hide. Note chimney breasts and window walls separately; the area above and below a window uses short drops that come from roll offcuts.
Buy the whole job in one batch
Confirm the same batch number on every roll before opening anything, keep one spare roll sealed for repairs, and photograph the label — if you ever need more, the batch and pattern numbers are the whole conversation with the store.
Frequently asked questions
What is a double roll?
A double roll is twice the length of a single roll in one package. Stores price it as one item but it covers two singles' worth — halve single-roll counts when buying doubles, rounding up.
Can I hang wallpaper on a freshly plastered wall?
Size or prime the wall first with wallpaper primer or diluted paste as the paper manufacturer directs. Bare plaster drinks the paste unevenly and seams open as it dries.