Tiling is bought in whole tiles and whole boxes, not in an exact number of square metres. The Tile calculator therefore separates room area, waste allowance, tile format and box size.
For 18 m² with 10% waste, plan 19.8 m². A 60 × 60 cm tile covers 0.36 m², so at least 55 tiles are required. If a box contains four tiles, you need 14 boxes: 56 tiles or 20.16 m² actually purchased.
Choosing the allowance
A simple rectangular room with a straight layout usually wastes less than a diagonal layout, many corners or a complex pattern. Large tiles can also create sizeable unusable offcuts. Start with a reasonable percentage and adjust it to the actual layout.
The calculator estimates quantity; it does not replace a detailed tile layout. For a visually sensitive room, plan the axes and edge cuts before final ordering.