# How much wallpaper do I need?

Works out how many rolls of wallpaper a room needs from its size, the roll width and length, and the pattern repeat, by counting the strips each roll gives.

- Page: https://www.acalculator.org/construction/wallpaper-calculator
- JSON spec: https://www.acalculator.org/construction/wallpaper-calculator.json
- Version: 948d803bbc05

## Default answer

Example with the default inputs (Room length 12 ft, Room width 12 ft, Wall height 8 ft, Roll width 20.5 in, Roll length 33 ft, Pattern repeat 0 in, Doors and windows 2, Spare rolls 1): A 12 ft × 12 ft room with 8 ft walls needs 9 rolls (29 strips, 4 per roll).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| l | Room length | The length of the room, wall to wall. |
| w | Room width | The width of the room, wall to wall. |
| h | Wall height | The height to paper, floor (or baseboard) to ceiling. |
| rw | Roll width | The width of the paper on the roll: 20.5 in on most US rolls. |
| rl | Roll length | The length of paper on one roll: 33 ft on a US double roll. |
| rep | Pattern repeat | The height of one repeat of the pattern; 0 for a free match or plain paper. |
| open | Doors and windows | How many ordinary-size doors and windows the walls have; every 4 save one roll. |
| spare | Spare rolls | Extra rolls for pattern matching, mistakes and later repairs. |
| p | Price per roll | Optional: what one roll costs, to total the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| rolls | Rolls to buy | The rolls for the strips, less one per 4 doors or windows, plus the spare rolls. |
| strips | Strips (drops) | The room perimeter ÷ the roll width, rounded up. |
| drop | Length of each strip | The wall height, rounded up to whole pattern repeats. |
| perRoll | Strips per roll | How many whole strips one roll gives: roll length ÷ strip length, rounded down. |
| area | Wall area | The room perimeter × the wall height, with no deduction for doors or windows. |
| cost | Total cost | Rolls to buy × the price per roll. |

## Method

Strips = ⌈2 × (length + width) ÷ roll width⌉; strip length = wall height rounded up to whole repeats; strips per roll = ⌊roll length ÷ strip length⌋; rolls = max(1, ⌈strips ÷ strips per roll⌉ − ⌊doors and windows ÷ 4⌋) + spare rolls.

## Assumptions

- The room is a rectangle and every wall is papered to the same height.
- Each strip starts at the same point of the pattern, so it is the wall height rounded up to whole repeats; leftover paper on a roll shorter than a strip is waste.
- Every 4 ordinary-size doors or windows save one roll (Brewster’s rule); larger openings are not deducted.
- One spare roll by default, as Cole & Son advise, for matching and mistakes. Buy all rolls from the same batch (dye lot).

## Worked examples

1. l = 3.6576, w = 3.6576, h = 2.4384, rw = 0.5207, rl = 10.0584, rep = 0, open = 2, spare = 1 gives strips = 29, perRoll = 4, rolls = 9, area = 35.674767. Source: Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary doors or windows), https://www.brewsterwallcovering.com/wallpaper-calculator, retrieved 2026-10-02; Cole & Son, Wallpaper Calculator (add an extra roll for pattern matching and waste), https://cole-and-son.com/pages/wallpaper-calculator, retrieved 2026-10-02.
2. l = 4.2672, w = 3.048, h = 2.7432, rw = 0.5207, rl = 10.0584, rep = 0.5334, open = 4, spare = 1, p = $60.00 gives strips = 29, drop = 3.2004, perRoll = 3, rolls = 10, cost = $600.00. Source: Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary doors or windows), https://www.brewsterwallcovering.com/wallpaper-calculator, retrieved 2026-10-02; Cole & Son, Wallpaper Calculator (add an extra roll for pattern matching and waste), https://cole-and-son.com/pages/wallpaper-calculator, retrieved 2026-10-02.
3. l = 4, w = 3, h = 2.5, rw = 0.53, rl = 10.05, rep = 0.64, open = 0, spare = 0 gives strips = 27, drop = 2.56, perRoll = 3, rolls = 9.
4. l = 6.2484, w = 6.2484, h = 2.4384, rw = 0.5207, rl = 10.0584, rep = 0, open = 0, spare = 0 gives strips = 48, rolls = 12.

## FAQ

### How do I work out how many rolls of wallpaper I need?

Count strips, not square feet. Divide the distance around the room by the roll width to get the strips, and the roll length by the wall height to get the strips per roll. A 12 × 12 ft room is 48 ft around: 576 in ÷ 20.5 in = 28.1, so 29 strips. A 33 ft roll gives 4 strips of 8 ft, so 29 ÷ 4 = 7.25, which is 8 rolls, plus a spare.

### Why not just divide the wall area by the roll area?

Because the paper is cut into strips the height of the wall, and the end of each roll that is too short for a strip is wasted. A 33 ft roll covers about 56 ft², but on 8 ft walls only 32 ft of it hangs. The strip method counts this waste.

### How does the pattern repeat change the number of rolls?

Each strip has to start at the same point of the pattern, so its length rounds up to whole repeats. With a 21 in repeat on 9 ft (108 in) walls, each strip takes 6 repeats, 126 in, and a 33 ft roll gives 3 strips instead of 3.67.

### Should I subtract doors and windows?

Only a little. Brewster’s rule is to take off one roll for every 4 ordinary-size doors or windows. Small openings still use up most of a strip, so many decorators do not subtract them at all.

### How many spare rolls should I buy?

At least one, as Cole & Son advise, for matching the pattern and fixing mistakes. Buy all the rolls at once from the same batch (dye lot), because a later batch can differ in colour.

### What size is a roll of wallpaper?

Sizes vary by maker, so check the label. A common US double roll (bolt) is 20.5 in wide and 33 ft long, about 56 ft². Milton & King rolls are 2 ft wide and 32.9 ft long. Many European rolls are about 0.53 m wide and 10 m long.

## Sources

- Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary-size doors or windows; larger repeats need more rolls), retrieved 2026-10-02. https://www.brewsterwallcovering.com/wallpaper-calculator
- Cole & Son, Estimate How Many Rolls of Wallpaper You Will Need (add an extra roll for pattern matching and waste), retrieved 2026-10-02. https://cole-and-son.com/pages/wallpaper-calculator
- Milton & King, How Many Wallpaper Rolls Do I Need? (rolls 2 ft × 32.9 ft; measure each wall; doors and windows count as waste), retrieved 2026-10-02. https://www.miltonandking.com/blog/how-many-wallpaper-rolls-do-i-need-how-to-measure-the-room/