Tiles, boxes, and budget for a given surface area and tile size.
Add more waste % for diagonal layouts (15%) or hex/herringbone (20%). Always buy from the same lot to avoid colour mismatch.
Buying tiles is a one-shot decision. Run short halfway through laying a bathroom floor and you face two bad options: the supplier's stock has rotated, the new lot's colour is microscopically off (a problem nobody notices until the floor is dry), or the product is discontinued and you cannot finish without a visible seam. The remedy is to calculate the right number once, with a generous waste margin that accounts for cutting losses near walls, breakage during transport, and the extra spares you will absolutely need eight years later when one corner cracks. This calculator turns three numbers — surface area, tile dimensions, and waste percentage — into the precise tile count, the box count (rounded up to the supplier's box size), and the total cost. It also reports how many spare tiles end up unused, useful for planning the post-job storage of replacements.
Tiles needed = ceil(area × (1 + waste/100) / single_tile_area), where single_tile_area = (tile_width_cm × tile_height_cm) / 10 000 to convert square centimetres to square metres. Box count = ceil(tiles / per_box). Actual area covered = tiles × single_tile_area, which exceeds the original area by the waste margin and the rounding-up to whole tiles and whole boxes. Cost = actual_area × price_per_m². Spare tiles after the job = tile_count − ceil(area / single_tile_area), which represents the genuinely-spare tiles to store for future repairs (the cutting waste is consumed during the job and is not part of "spare"). The 10 % default waste margin is a sensible starting point for a straight grid layout on a rectangular floor with no unusual obstacles. Increase to 15 % for diagonal layouts (more cuts, larger triangular offcuts), to 20 % for hexagonal or herringbone patterns (significant cutting losses), and to 25 % for floors with multiple obstacles (toilet flanges, columns, irregular walls). The tool exposes the waste percentage as a free input so the user can pick what matches their layout.
Six inputs: surface area in square metres (the room dimensions multiplied), waste percentage, tile width and height in centimetres, tiles per box (the supplier label, typically 6, 8, or 10 for large-format tiles and 30+ for small mosaic tiles), and price per square metre. Defaults represent a 20 m² living-room floor with 60 cm × 60 cm large-format tiles, 6 per box, at €25/m² — a realistic mid-range budget tile. The result panel shows the tile count, the box count, the actual coverage area, the spare tiles for future repairs, and the total cost. The tile count and box count adjust live as inputs change — slide the waste percentage from 10 to 20 % and watch the box count jump.
A 20 m² living room floor with 60 × 60 cm tiles, 6 per box, at €25/m², 10 % waste. Single tile = 0.6 × 0.6 = 0.36 m². Area with waste = 20 × 1.10 = 22 m². Tiles = ceil(22 / 0.36) = ceil(61.1) = 62. Boxes = ceil(62 / 6) = 11 (which provides 66 tiles — three additional rounded up by box size). Actual coverage = 66 × 0.36 = 23.76 m². Cost = 23.76 × 25 = €594. Spare = 66 − ceil(20 / 0.36) = 66 − 56 = 10 tiles. Now consider a smaller bathroom: 6 m² with 20 × 20 cm tiles, 25 per box, at €40/m², 15 % waste. Single tile = 0.04 m². Area with waste = 6.9 m². Tiles = ceil(6.9 / 0.04) = 173. Boxes = ceil(173 / 25) = 7 (175 tiles total). Cost = 175 × 0.04 × 40 = €280. Spare = 175 − 150 = 25 tiles — a generous spare from the box rounding alone, useful in a bathroom where one cracked tile is hard to replace. The two examples illustrate the asymmetry: large-format tiles produce small spare counts; small-format tiles produce large ones because the per-box quantity is bigger.
First, computing the bare area without waste. Cut tiles produce triangular offcuts that cannot be reused; the floor near the walls and around obstacles needs a margin. Even on a perfectly rectangular room with no obstacles, the cutting waste is 5–8 %. Second, mixing tile lots. Tile production batches differ slightly in colour and dimensions; supplies bought from different lots placed adjacent on the same floor produce visible differences. Buy from the same lot — note the lot number on the box — and buy a few extra spares to outlast future supply changes. Third, ignoring the box-rounding. You cannot buy 7.3 boxes; you buy 8. The calculator rounds up; many online tools just give the tile count, leaving the buyer to do the rounding manually. Fourth, forgetting grout-line gap. Grout lines (typically 2–5 mm) increase the effective tile span slightly. For 60 × 60 cm tiles with 3 mm grout, the actual centre-to-centre spacing is 60.3 cm — meaning the floor needs 0.5 % fewer tiles than the bare-tile math suggests. The calculator ignores this; it is dwarfed by the waste margin. Fifth, confusing facial dimension with nominal dimension. Some tile manufacturers list a 60 × 60 product whose actual face is 597 × 597 mm; the missing 3 mm per side is the manufacturing tolerance. The grout fills the gap. The calculator uses the listed facial dimension, which matches the convention.
Tile installation has many sub-genres. Large-format porcelain (60 × 120, 80 × 80, 120 × 240) is the dominant trend in residential floors and walls; cuts are harder and waste % climbs to 15 %. Subway tiles (10 × 30, white-bodied ceramic) for bathrooms and kitchens — small, high tile count, low waste. Hexagonal tiles for entryways and feature walls — irregular boundaries, 20 % waste. Herringbone patterns with rectangular tiles — significant cutting at all four walls, 20 % waste. Outdoor pavers at 40 × 40 or 50 × 50 with 5 mm gaps — same math, lower price per m² (€15–25 for porcelain, €5–10 for concrete). Rectified tiles (precision-cut edges) allow grout lines as narrow as 2 mm and a near-seamless look; non-rectified tiles need 3–5 mm grout to absorb dimensional tolerance. Tile thickness affects substrate prep: 8 mm tiles work on standard substrates; 20 mm structural pavers need a thicker mortar bed and can replace a slab. None of these change the core math the calculator implements; they change the inputs and the waste percentage you should pick.