DIY Home CalcsWallpaper Calculator
Work out how many rolls of wallpaper to buy using the strip method decorators use. Enter the total width of the walls, their height, the roll size and the pattern repeat from the label.
How the strip method works
- Strip length. Take the wall height and add about 4 in (2 in at top and bottom for trimming). If the paper has a pattern repeat, round that length up to a whole number of repeats so every strip can be matched.
- Strips per roll. Divide the roll length by the strip length and round down. Only full strips count.
- Strips needed. Divide the total wall width by the roll width and round up.
- Rolls. Divide strips needed by strips per roll and round up.
rolls = ⌈⌈wall width × 12 ÷ roll width⌉ ÷ strips/roll⌉
Worked example
A 12 × 12 ft room with 8 ft walls, papered with 20.5 in × 33 ft rolls that have a 21 in repeat:
- Strip length: 96 + 4 = 100 in, rounded up to 5 repeats = 105 in.
- Strips per roll: 396 in ÷ 105 = 3.77, so 3 strips.
- Strips needed: 576 in ÷ 20.5 in = 28.1, so 29 strips.
- Rolls: 29 ÷ 3 = 9.7, so buy 10 rolls.
With a plain or random-match paper (no repeat), each strip is 100 in and you still get 3 strips per roll (396 ÷ 100 = 3.96), so the answer is the same here. The count changes most with large repeats, tall walls and short rolls.
Wallpaper buying tips
- Check the batch number. Buy every roll from the same batch (lot) so the color matches, and buy one extra roll for mistakes and future repairs.
- Accent wall only? Enter the width of that one wall. A 12 ft accent wall with 8 ft ceilings typically takes 3 to 4 rolls.
- Drop match vs straight match. Drop-match patterns offset every other strip by half a repeat; the strip method above already allows for a full repeat, which covers both.
- Prep the walls. Prime new drywall with a wallpaper primer so the paper can be removed later without damaging the surface.
- Painting the other walls? Use the paint calculator and set the width to 0 to measure single walls.
Frequently asked questions
How many rolls of wallpaper do I need for a room?
Add up the width of every wall you will paper, divide by the roll width to get the number of strips, then divide by how many full-height strips you can cut from one roll. For a typical 12 × 12 ft room with 8 ft walls and a 21 in pattern repeat, that is about 10 standard 20.5 in × 33 ft rolls.
What is a pattern repeat?
It is the vertical distance before the design repeats itself, printed on the label. Each strip must start at the same point in the pattern, so a large repeat means more waste per strip and fewer strips per roll.
Why not just divide the wall area by the roll area?
Because you can only use whole, full-height strips. Leftover pieces shorter than the wall are mostly waste. The strip method used here counts strips, so it is more accurate than an area estimate, especially with big pattern repeats.
Should I subtract doors and windows?
Usually not for the strip count. Strips above doors and below windows still use roll length, and offcuts rarely match. For a room with very large openings, you can subtract the width of those openings from the total wall width.
What size is a standard roll of wallpaper?
Many rolls sold in the US and Europe are about 20.5 to 21 in wide and 33 ft long (0.53 × 10.05 m), covering around 56 sq ft. Always use the dimensions on your roll's label; some designer and grasscloth papers are 27 or 36 in wide.