Count the tiles and boxes for a floor or wall from the area, tile size, grout gap and waste allowance.
Tiles needed
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Tiles = area ÷ ((tile length + joint) × (tile width + joint)) × (1 + waste %)
Tiling a wall? Measure each wall's width × height, subtract windows and doors, and add the areas together before entering them as length × width (for example, total area × 1).
Pouring a new base first? See the concrete calculator.
Divide the area to tile by the area of one tile including its grout joint, then add extra for cuts and breakage. For a 3 × 4 m floor (12 m²) with 30 × 30 cm tiles and 3 mm joints, each tile covers 0.303 × 0.303 = 0.0918 m², so you need 131 tiles, or 144 with 10% extra.
10% for simple rooms with straight layouts, 15% for rooms with many corners, and 15–20% for diagonal or herringbone patterns, which need more cuts. Keep a few spare tiles for future repairs.
Slightly. Wider joints mean each tile covers a bit more area, so you need fewer tiles. With large tiles the difference is small; with small mosaic tiles it adds up.
Yes. Choose meters and centimeters, or feet and inches. Room sizes and tile sizes use the matching unit.