Good measurements are cheap; bad measurements are very expensive. It's extremely important to have accurate measurements of your wall, and to compensate for potentially sloped floors or ceilings.
It's important to measure your walls in more than one location and to add bleed. We recommend 1-inch extra on all four sides for safety, so a 90-inch tall wall would need a 92-inch print.
From Wallcoverings Association:
"The most important step in estimating wallcovering is accurate measurements. Use a yardstick or steel tape measure, never a cloth tape measure. Take measurements in feet rounding off to the next highest half foot or foot. Draw a room diagram showing doors, windows and ceiling height. If a wall is unusually broken up with a fireplace, built-in bookcases, etc., a diagram with detailed measurements will be beneficial in figuring square footage of wallcovering needed.
"Measure wall height from floor to ceiling. Exclude baseboards and moldings. Measure length of each wall including doors and windows. Find the total square feet of the wall(s) by multiplying ceiling height by total wall length. Subtract areas that will not be covered. (Standard doors are about 3 x 7 feet or 21 square feet; standard windows about 3 x 4 or 12 square feet.)
"These calculations give the total number of square feet to be covered. Using this the number of rolls or linear yards of wallcovering can be determined."