How many panels do I need?

Use the width from Measure your wall — your wall plus 4 cm (2 in).

Each panel is 72 cm (28 in) wide. Divide and round up to the next whole number.

Example: a 340 cm wall → 344 cm → 344 ÷ 72 = 4.78 → 5 panels.

If your result lands almost exactly on a whole number (5.02, for instance), add one panel — otherwise you'd have nothing left to trim.