Wallpaper Calculator

Wallpaper estimation requires measuring the total wall area, accounting for pattern repeat (which causes waste), subtracting doors and windows, and converting to the number of rolls based on the usable coverage per roll.

Core formula: Total Wall Area = Perimeter × Wall Height (minus doors and windows) Rolls Needed = Total Wall Area × Waste Factor ÷ Roll Coverage

This calculator works from area rather than counting individual strips. Area is the more forgiving method for a first estimate, and the waste factor is what absorbs the pattern matching. If you are buying an expensive paper with a big repeat, count strips by hand as a cross-check before you order.

What each variable means:

• Perimeter: total distance around the room (sum of all wall widths); includes walls that have doors/windows since you cut around them
• Wall Height: floor to ceiling
• Roll Coverage: the square footage one roll covers. Take it off the label rather than assuming, because roll sizes differ sharply by region (see the table below).
• Pattern Repeat: the vertical distance between identical points in the design. It does not enter the arithmetic directly, but it is what drives the waste factor: a bigger repeat means more length trimmed off each strip to make it line up with its neighbour.
• Waste Factor: 10% for a random match, rising to 25% or more for a large or drop-matched repeat

Worked example: Room: 15’ × 12’, ceiling height 9’. Two doors and two windows. Straight-match paper. US double rolls at 60.75 sq ft each.

Perimeter = 2 × (15 + 12) = 54 linear feet Gross wall area = 54 × 9 = 486 sq ft Openings: 2 doors × 21 + 2 windows × 15 = 72 sq ft Net area = 486 − 72 = 414 sq ft With 15% straight-match waste = 414 × 1.15 = 476 sq ft Rolls = 476 ÷ 60.75 = 7.8 → 8 double rolls

The roll figure is the one that trips people. A US “single roll” is only about 30 sq ft, and almost nothing is actually sold that way. Retail packs are double rolls at roughly 60 sq ft, so quoting a job in single rolls and buying in doubles is how people end up with half what they need.

Always order extra. Dye lots vary between production runs, and discontinued patterns become unavailable.

Standard roll sizes by region

In US home centers, what’s labeled “one roll” is almost always a double roll. Check carefully; labeling varies between sellers, and buying based on the wrong assumption can leave you 50% short.

Waste factor by pattern type

The pattern repeat costs you length on every strip because each strip after the first must align with its neighbor. A 24-inch repeat on a 9-ft wall wastes about 24 inches per strip, almost 25% loss before counting offcuts around doors and windows.