How to calculate wallpaper
wall area = 2 × (length + width) × height
rolls = ceil((net area × (1 + waste%)) ÷ usable roll area)
Example: 12×14 room, 8-ft walls, 1 door, 2 windows, 12" repeat
- Perimeter: 2 × (12 + 14) = 52 ft
- Wall area: 52 × 8 = 416 sq ft
- Subtract 1 door (20) + 2 windows (30) = 366 sq ft net
- Apply 15% waste factor: 366 × 1.15 = 421 sq ft
- Each strip is cut 8 ft + 12 in = 9 ft, so a 20.5 in × 33 ft roll gives 3 strips covering 41.0 sq ft of wall
- Rolls needed: 421 ÷ 41.0 = 10.3 → 11 single rolls (6 double)
Standard wallpaper roll sizes
Typical sizes, not an official standard; the width and length printed on your roll are what count. Coverage is the roll's face area, width × length.
| Type | Width | Length | Coverage |
|---|---|---|---|
| US single roll | 20.5" | 33 ft | 56.4 sq ft |
| US double roll | 20.5" | 66 ft | 112.8 sq ft |
| European standard | 21" | 33 ft | 57.8 sq ft |
| Wide roll | 27" | 27 ft | 60.8 sq ft |
| Commercial grade | 54" | 30 yd | 405 sq ft |
Makers don't all use single and double roll the same way, so check the dimensions. Usable coverage is less than the face area because each strip is cut to the wall height plus the repeat: on an 8 ft wall a 20.5 in × 33 ft roll gives 4 strips covering 54.7 sq ft with no repeat, and 3 strips covering 41.0 sq ft with a 12 in repeat.
Pattern repeat explained
The waste figures are trade rules of thumb, not a standard. The calculator handles the repeat itself by lengthening each strip, so your waste percentage only needs to cover trimming and mistakes.
| Pattern type | Description | Waste |
|---|---|---|
| Random / no match | Texture, stripes, solid colors, no alignment needed | 5–10% |
| Straight match | Pattern lines up horizontally across strips | 10–15% |
| Drop match (half) | Pattern shifts halfway down on adjacent strips | 15–20% |
| Large repeat (20"+) | Big motifs, highest waste due to alignment | 20–25% |
How to measure a room for wallpaper
- Measure each wall's width and add them up for the total perimeter. Don't skip alcoves or chimney breasts, measure their sides separately and add.
- Measure the wall height from top of baseboard to bottom of ceiling/crown molding.
- Multiply perimeter × height for gross wall area.
- Subtract openings: the calculator allows 20 sq ft for a typical door and 15 sq ft for a window, or measure yours. Small openings can be ignored.
- Add waste: rules of thumb run from about 10% for solid or random papers to 20% or more for large patterns.
- Divide by usable roll coverage: whole strips per roll × wall height × roll width. On an 8 ft wall with no repeat that is 54.7 sq ft for a 33 ft roll and 109.3 sq ft for a 66 ft roll.
- Round up to the nearest whole roll, and order one extra.
Wallpaper vs paint
| Feature | Wallpaper | Paint |
|---|---|---|
| Materials cost | Enter your price per roll above | See the paint calculator |
| Install | Slower: strips cut, matched and hung | Faster: rolled or brushed on |
| Cleanability | Wipe-clean vinyls | Depends on sheen |
| Removal difficulty | Moderate (steam + score) | Easy (sand + repaint) |
| Design variety | Thousands of patterns | Infinite colors, limited texture |
How much wallpaper waste to expect
Rules of thumb from the trade, not a standard; follow the maker's hanging instructions where they differ.
- No pattern (solid or texture), 5–10% waste from trimming at ceilings, baseboards, and corners.
- Small repeat (< 8 inches), 10–15% waste from pattern matching between strips.
- Medium repeat (8–18 inches), 15–20% waste.
- Large repeat (> 18 inches), 20–25% waste. Drop-match patterns are the worst.
- Complex rooms (angles, alcoves, sloped ceilings), add another 5–10%.
Keep at least one extra roll for future repairs, wallpaper dye lots change between production runs and are nearly impossible to match later.
Frequently asked questions
How many rolls of wallpaper do I need?
Take the room's perimeter times the wall height, remove the doors and windows, add a waste allowance, and divide by what one roll really covers once each strip is cut to length. In the 12 by 14 foot example with 8-foot walls and a 12-inch repeat, that is 366 sq ft net, 421 with 15% waste, and 41.0 sq ft per 20.5 in × 33 ft roll: 11 single rolls, or 6 doubles. The roll's face area, 56.4 sq ft, overstates it because offcuts are lost.
What is wallpaper pattern repeat?
It's how far down the paper you go before the design starts again, printed on the label as the repeat. A 6-inch repeat means the motif recurs every 6 inches. Neighbouring strips have to line up, so each one is cut longer than the wall and the extra is thrown away; bigger repeats throw away more. Enter the repeat in the calculator and it lengthens every strip by that much.
What size is a standard roll of wallpaper?
There is no official standard, and makers don't all use the words 'single' and 'double' the same way, so go by the width and length on the label. A common size is 20.5 inches × 33 feet, 56.4 sq ft of face. On 8-foot walls that roll gives 4 full strips with no repeat, covering 54.7 sq ft; a 66-foot bolt gives 109.3. Wider and commercial rolls exist too.
How do I calculate wallpaper for a feature wall?
Width × height gives the area: a 12-foot wall 8 feet high is 96 sq ft, or 110.4 with a 15% allowance. With no pattern repeat a 20.5 in × 33 ft roll covers 54.7 sq ft of that wall, so you need 3 single rolls (2 double). A large repeat cuts each roll's yield, so enter it if your paper has one.
Should I buy extra wallpaper?
Yes, one roll more than the calculation is sensible. A later order may come from a different print batch and not quite match, a strip can tear or be cut wrong, and a spare lets you patch damage later. Check that every roll carries the same batch or lot number before you start hanging. Store leftovers rolled, somewhere dry.
What is the difference between a single and double roll?
A double roll is one continuous piece twice the length of a single, so a 20.5 in × 66 ft double has 112.8 sq ft of face against 56.4 for a 33-foot single. Prices are sometimes quoted per single roll even when the paper only comes in doubles. The longer piece can waste less, since there are fewer short ends left over when strips are cut.
How do I account for pattern matching waste?
Cut each strip one repeat longer than the wall is high, so it can slide up or down to line up with its neighbour. A 96-inch wall with a 12-inch repeat needs 108-inch strips, and up to 12 inches of each goes in the bin: 11.1% of the paper. The calculator applies that per strip; your waste percentage then covers trimming and mistakes on top.
How much wallpaper for a 10x12 room?
With 8-foot walls, one door and two windows: a 44-foot perimeter gives 352 sq ft of wall, 302 after the openings. With a 12-inch repeat and 15% waste you need 347 sq ft at 41.0 sq ft a roll: 9 single rolls (5 double). A plain paper with 10% waste gets 54.7 sq ft from each roll, so 7 singles (4 double). Add a spare either way.