Wallpaper planner

One wall or four equal-height walls of a rectangular room. Count full-height strips separately for each wall: ceil(wall width / roll width), then sum. Corner offcuts are not reused across walls. Doors/windows are not deducted as full-height widths: their position and pieces above/below would require an actual layout. This is a conservative full-strip plan, not the minimum paper purchase.

Cut length C = wall height + total top/bottom trim in cm / 100. The 10 cm initial trim is an example, not per end. No-pattern cuts follow directly. For straight repeat R in metres, start spacing S = ceil(C/R) × R. For exactly half-drop, S = (ceil(C/R − 0.5) + 0.5) × R; alternate A/B starts differ by R/2. Each strip is C long; gaps between starts account for matching.

Roll lead is the amount discarded from each roll before the same reference phase A. Zero assumes the roll already begins at that phase; measure/allow the actual lead, do not assume different rolls start identically. A phase-B start uses another R/2. Available strips = max(0, floor((roll length − lead − phase offset − C)/S) + 1). The last strip needs only C, not an extra full matching interval.

Strips are cut and hung sequentially; half-drop phase continues across rolls and walls. A/B capacities and count parity determine how many rolls are consumed. The sketch shows the first two rolls, with up to five individual strips and later strips grouped. No grouped A/B cutting optimization, offcut reuse, unequal heights, reverse hanging, arbitrary offsets, defects, corner overlap or product-specific rules. Add whole spare rolls if desired; no automatic percentage.

Calculate/Enter; edits clear output. Reset restores examples and free-match mode. Software bounds and safe counts only; no storage. Consult the actual roll insert for repeat/offset and preparation. Erismann nonwoven hanging tips (2009) describes trim, identical straight-match strips and alternating offset; it does not supply our cutting formula.