How to use
- Enter a rectangular room or add individual walls. For walls with different heights, use separate rows.
- Enter the actual width and length of one supplied roll. Do not treat a marketing term such as “double roll” as a physical roll count.
- Select free, straight or half-drop match. For patterned paper, enter the vertical repeat from its label. Half-drop uses an offset of half that repeat.
- Enter the combined top and bottom trim. Optionally reserve one repeat per roll for matching its starting position, and add spare rolls.
- Set the number of physical rolls per pack and whether the price is per roll or pack. Review the cut groups and purchase quantity.
Metric uses metres for walls and roll length, and centimetres for roll width, repeat and trimming. US uses feet and inches. Changing currency relabels the entered price without converting it.
Calculation method
For each wall, divide its width by roll width and round up to full-width strips. Each wall starts with a fresh full-width strip; partial widths are not carried around corners.
The required drop is wall height + total trim. The planned blank length is:
- Free match: required drop.
- Straight match: required drop rounded up to a multiple of the repeat.
- Half-drop: required drop + half a repeat, then rounded up to a multiple of the repeat.
The half-drop rule deliberately reserves a conservative blank rather than optimising alternate strips. If start alignment is selected, one full repeat is reserved from every roll. Divide the remaining usable roll length by blank length and round down to find whole strips per roll.
Walls with the same planned blank length share a cut group. Each group rounds its roll count up separately; different cut lengths do not share rolls or offcuts. Spare rolls are added before rounding to full packs.
A worked example
A 4 × 3 m room with 2.4 m walls has two walls of each width. With a 0.53 m roll width, each 4 m wall needs 8 strips and each 3 m wall needs 6: 28 strips altogether.
For free-match paper with 0.10 m total trim, each blank is 2.50 m. A 10.05 m roll provides 4 whole blanks, so the estimate needs 7 rolls. With no spare rolls, one physical roll per pack and 45 USD per roll, the total is 315 USD.
Changing the match or repeat changes the planned blank length and can substantially increase the roll count.
Understanding your result
Doors and windows are not subtracted. Keeping full-height strips avoids assuming that an opening can save an entire usable strip. It may overestimate a project with large openings; a detailed hanging plan is needed to establish a smaller safe quantity.
The cut plan summarises blank lengths and capacities. It is not a numbered wall layout or a guarantee of the lowest possible roll count. Murals, matched A/B sets, stairs, sloped walls and nonstandard hanging schemes need a separate plan. Paste, preparation, labour, tax and delivery are excluded.
Read the wallpaper rolls and patterns guide to check the label, batch and hanging instructions before you buy.