perimeter: — ·
strip length: — ·
strips needed: — ·
strips per roll: —
rolls needed: —
rolls needed: —
How it counts
Perimeter = 2 × (length + width). A strip is the ceiling height plus 5 cm for trimming; with a pattern repeat the strip length is rounded up to a multiple of the repeat. Strips needed = perimeter ÷ roll width (rounded up), strips per roll = roll length ÷ strip length (rounded down). Windows and doors are usually not subtracted - offcuts go above the openings and into the spare.
Spare
Buy one roll beyond the calculation: batches differ in shade, and buying an identical roll later may be impossible. Check the batch number on the labels - it must match on every roll.