Tile count comes from two areas
A 30 cm by 30 cm tile covers 0.09 m². A 20 m² surface with 10% allowance becomes 22 m², and 22 divided by 0.09 is 244.44 tiles; whole pieces make the order 245. This is a face-area calculation, so it assumes the stated tile dimensions are appropriate for the installed joint pattern.
Grout joints alter the grid
Tiles do not normally touch edge to edge. A 3 mm joint makes each repeated module slightly larger than the fired tile face, while perimeter cuts absorb a different amount. For a precise setting-out plan, use the tile-plus-joint module and place the centreline; the simple count is best used as a purchasing baseline.
Cuts are shaped by the room
A square floor can use many opposite-edge offcuts. Niches, pipes, diagonal lines, borders, and patterned faces may make those pieces unusable. Keep breakage and selection in the allowance, especially with veined or directional porcelain where a visually acceptable cut cannot always be reused.
Thickness is not coverage
A thicker tile affects floor build-up, transitions, adhesive choice, and sometimes load, but not its visible square coverage. Likewise, wall tile and floor tile can have the same face area while requiring different substrates and products. Do not use a count estimate as an installation specification.
Where this count stops
This page converts a measured surface and tile face into a whole-piece quantity. It does not calculate adhesive bed depth, grout mass, waterproofing, movement joints, falls to a drain, or substrate deflection. Those are site and product questions that need the relevant installation instructions.
Set out full tiles before trimming
Snap perpendicular control lines and dry-lay a row across the most visible dimension. A layout that leaves a 20 mm sliver at one wall can often be centred to give balanced cuts at both sides, changing the number of pieces lost to trimming. Check the selected tile’s calibre and rectification before choosing joint width. This planning step belongs before opening boxes, not after the order is exhausted.
Inspection note: Set out full tiles before trimming
Before ordering or fitting, revisit this project-specific check: Snap perpendicular control lines and dry-lay a row across the most visible dimension; A layout that leaves a 20 mm sliver at one wall can often be centred to give balanced cuts at both sides, changing the number of pieces lost to trimming; Check the selected tile’s calibre and rectification before choosing joint width; This planning step belongs before opening boxes, not after the order is exhausted.