How to use the wallpaper calculator
- Choose whole room (enter length and width) or feature wall (enter the total width).
- Enter the wall height and the width of any doors you will skip.
- Choose your roll size and the pattern repeat from the label.
- Keep a trim allowance (about 2 in / 5 cm at the top and bottom) and at least one spare roll.
The strip (drop) method
Strips needed = Wall width ÷ Roll width → round up Strip length = Wall height + Pattern repeat + Trim Strips per roll = Roll length ÷ Strip length → round down Rolls = Strips needed ÷ Strips per roll → round up
Worked example
A 12 × 10 ft bedroom with 8 ft walls and US double rolls 20.5 in × 33 ft, plain paper:
- Wall width = 2 × (12 + 10) = 44 ft = 528 in → 528 ÷ 20.5 = 25.8 → 26 strips
- Strip length = 96 + 0 + 4 = 100 in → 396 ÷ 100 = 3.96 → 3 strips per roll
- Rolls = 26 ÷ 3 = 8.7 → 9 rolls, plus 1 spare = 10
With a large pattern repeat of 21 in, each strip is 121 in and a roll still gives 3 strips, so the answer stays at 9 rolls — but a 27 in repeat would drop it to 3 strips with more waste, and on some roll sizes to 2.
Typical roll sizes
| Roll | Width × length | Area |
|---|---|---|
| US double roll (narrow) | 20.5 in × 33 ft | 56 ft² |
| US double roll (wide) | 27 in × 27 ft | 61 ft² |
| European standard | 0.53 × 10.05 m | 5.3 m² (57 ft²) |
| Wide European | 0.70 × 10.05 m | 7.0 m² (76 ft²) |
Wallpapering tips
- Check the batch number on every roll and buy them all at once.
- Prime the walls with a wallpaper primer — it helps the paper slide into place and makes it easier to remove later.
- Start next to a door or in a corner and use a plumb line or laser for the first strip; walls are rarely straight.
- Hang the focal wall first so the most visible pattern match is perfect.
- Read the label symbols: paste-the-wall, paste-the-paper or pre-pasted papers each hang differently.
- Large patterns: centre the main motif on a feature such as a fireplace or headboard.
Single vs double rolls in the US
American wallpaper is usually priced per single roll but only sold in double rolls (bolts). If a listing says “sold as a double roll,” the price shown may be for half of what you receive. Always compare the total square feet and the price per double roll before ordering, and enter the real width and length of the bolt as a custom roll when it differs from the presets.