Tile calculator: tiles and boxes for a floor or wall from room size, tile size, grout joint and waste allowance, plus grout in litres and kg.
12 m² takes about 65.7 tiles laid edge to edge; with 10% for cuts and breakage buy 73 tiles, which is 10 boxes of 8. The joints need about 2.6 kg of grout.
Rounded up to whole tiles.
Rounded up to whole boxes.
Lengths in mm give litres of joint per m². 1.6 kg/L is Mapei's factor for cementitious grout; the estimate has no waste added.
The tile count is the area divided by the area one tile covers with its grout joint, (tile length + joint) × (tile width + joint). A waste allowance for cuts and breakage is added, then the count is rounded up to whole tiles and whole boxes. Grout volume per m² is (A + B) ÷ (A × B) × tile thickness × joint width, with A and B the tile sides and all four in millimetres.
The default 4 × 3 m floor in 600 × 300 mm tiles with 3 mm joints takes 65.7 tiles laid edge to edge. With 10% waste that is 73 tiles, or 10 boxes of 8, plus 1.62 L of grout (2.6 kg).
The waste presets are this calculator's rules of thumb: 10% for a straight lay, 15% for diagonal and 20% for herringbone, which cut more tiles at the edges. The drawing shows a straight lay.
Checked against: Python decimal: 12 ÷ (0.603 × 0.303) = 65.68 × 1.1 = 72.25 → 73; grout (900/180000) × 9 × 3 × 12 = 1.62 L × 1.6 kg/L (Mapei formula); 10 boxes × 40 = 400
Checked against: Python decimal: 120 ft² ÷ (12.125 in)² = 117.54 × 1.15 = 135.17 → 136 tiles → 14 boxes of 10; Mapei grout formula in mm
Checked against: Hand calculation: 3 m ÷ 0.3 m = 10 tiles each way = 100 tiles, 10 boxes; a zero-width joint needs no grout
Divide 1 m² by the area of one tile plus its joint. A 600 × 300 mm tile with a 3 mm joint covers 0.603 × 0.303 = 0.1827 m², so 1 m² takes 5.47 tiles; 300 × 300 mm tiles take 10.89. Multiply by the whole area before rounding up: rounding 5.47 up to 6 per m² would overbuy by about 10%.
About 98 twelve-inch tiles before waste. A 12 × 12 in tile with a ⅛ in joint covers 12.125 × 12.125 in, or 1.021 ft², so 100 ft² takes 97.95 tiles. Adding 10% for cuts and breakage gives 107.7, rounded up to 108 tiles.
This calculator's presets add 10% for a straight lay, 15% for a diagonal lay and 20% for herringbone, because angled layouts cut more tiles along every wall. On the default 12 m² floor those give 73, 76 and 79 tiles of 600 × 300 mm.
Multiply (A + B) ÷ (A × B) by tile thickness and joint width, all in mm, to get litres of joint per m². For 600 × 300 mm tiles 9 mm thick with 3 mm joints that is 900 ÷ 180,000 × 9 × 3 = 0.135 L per m², or 1.62 L for 12 m². The calculator converts at 1.6 kg per litre; check the grout bag's own coverage table.
Yes, they lower it slightly, because each tile plus its joint covers more floor. A 600 × 300 mm tile covers 0.18 m² on its own and 0.1827 m² with a 3 mm joint, so 12 m² needs 65.7 tiles instead of 66.7 before waste. For 50 × 50 mm mosaic with 3 mm joints, each tile's footprint grows by 12.4%.
Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “4 × 3 m floor, 600 × 300 mm tiles, 3 mm joints, 10% waste” is checked against Python decimal: 12 ÷ (0.603 × 0.303) = 65.68 × 1.1 = 72.25 → 73; grout (900/180000) × 9 × 3 × 12 = 1.62 L × 1.6 kg/L (Mapei formula); 10 boxes × 40 = 400.
Mapei grout calculator — consumption (A + B)/(A × B) × C × D × 1.6 = kg/m²; TCNA Handbook for Ceramic, Glass, and Stone Tile Installation — joint widths and layouts.
3 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.
Floor area in square metres and square feet, wall area, perimeter and volume for one or more rectangular rooms or an L-shaped room.
Calculate concrete volume and bags for slabs, footings, columns or steps. Compare bag and ready-mix quotes with delivery fees, minimums and order increments.
Deck boards, joists and screws or hidden clips for a rectangular deck, from its size, joist spacing, board width, gap and waste allowance.
Paint calculator: litres, US gallons and whole cans of paint and primer for a room, from wall area minus doors and windows, coats and coverage.
Drywall sheets for a room's walls and ceiling after doors and windows, with screws, joint tape and compound, for 4 × 8 ft or metric plasterboard.
Wallpaper calculator: rolls to buy from wall width and height, roll size, pattern repeat and trimming, counted as full-height drops per roll.
Allow optional Google Analytics to measure page visits? Calculators work either way. Privacy and choices
Optional analytics: off.