Step 1: measure the wall
Measure the width and the height of the wall in millimetres. If the wall is up to 2.8 m high, one sheet covers the full height. Note any doors, windows and sockets, and every edge where the panelling will stop.
Step 2: count the sheets
Divide the width of the wall by 1100 mm and round up. A wall 4000 mm wide needs 4000 ÷ 1100 = 3.64, so 4 sheets across. If the wall is 2600 mm high, each sheet is cut down by 200 mm.
Check the result by area: 4.0 m × 2.6 m = 10.4 m², and 10.4 ÷ 3.08 = 3.4 sheets, which again rounds up to 4. Four sheets are 12.32 m², and that is the quantity to order.
Panels in 1220 × 2800 mm sheets (3.416 m²: the SPC panel and the 18 mm WPC board) and the 1220 × 2440 mm fireproof panel (2.977 m²) are worked out in the same way with their own sizes.
Step 3: allow for openings and cuts
Doors and windows rarely reduce the number of sheets, because the offcuts around them are often too narrow to reuse. Count full sheets across the wall first, then deduct a sheet only where an opening takes up a sheet's full width. If the wall is irregular, or you are following a seam pattern, add a spare sheet.