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.
By AdminDrafted with AI writing toolsUpdated Checked examples: 3
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.
Divide the floor or wall area by the area of one tile plus its grout joint, add a waste allowance, then round up to whole tiles and whole boxes. A 10 × 8 ft floor in 12 × 12 in tiles with ⅛ in joints takes 78.4 tiles edge to edge, or 87 tiles with 10% waste.
Metric tiles work the same way. A 600 × 300 mm tile with a 3 mm joint occupies 603 × 303 mm, or 0.182709 m², so a 4 × 3 m floor takes 65.68 tiles, 73 with 10% waste.
The waste percentage covers cut edges and breakage. Rules of thumb are 10% for a straight lay, 15% for a diagonal lay and 20% for herringbone, because angled patterns cut more tiles along each wall.
Box rounding adds its own spares. On the 4 × 3 m floor, 73 tiles need 10 boxes of 8, which hold 80 tiles; adding 10% again on top of those 7 extra tiles double-counts the allowance.
One tile past a box boundary buys a whole box. A 2.4 × 1.2 m area in 600 × 300 mm tiles, with no joint and no waste, takes exactly 16 tiles: two boxes of 8. A 17th tile would need a third box.
Grout volume in liters per square meter is (A + B) ÷ (A × B) × tile thickness × joint width, with the tile sides A and B and the other two dimensions all in millimeters.
Small tiles have far more joint per square meter. 600 × 300 mm tiles 9 mm thick with 3 mm joints need 0.135 L per m². 25 × 25 mm mosaic at the same depth with 2 mm joints needs 1.44 L per m², 10.7 times as much.
On a 12 m² floor that is 1.62 L of grout for the large tiles and 17.28 L for the mosaic. At 1.6 kg per liter, the consumption factor in Mapei's Ultracolor Plus technical documentation, those weigh 2.59 kg and 27.65 kg.
That factor belongs to one product family, so check your own grout's coverage table. The grout figure carries no waste allowance of its own.
The first four rows are the 4 × 3 m floor in 600 × 300 mm tiles, with 3 mm joints, 10% waste and boxes of 8, unless the name says otherwise. "Zero joint" drops both the joint and the waste. "Exact box" is the 2.4 × 1.2 m area described above.
| Scenario | Tiles | Boxes of eight | Grout, kg |
|---|---|---|---|
| Default | 73.000000 | 10.000000 | 2.592000 |
| No waste | 66.000000 | 9.000000 | 2.592000 |
| Herringbone allowance | 79.000000 | 10.000000 | 2.592000 |
| Zero joint | 67.000000 | 9.000000 | 0.000000 |
| Exact box | 16.000000 | 2.000000 | 0.000000 |
Removing the joint raises the count from 66 to 67, because each tile then covers less floor. The waste allowance never changes the grout, which depends only on the joints in the measured area.
For an L-shaped room or several rooms, add up the floor area with the room area calculator first.
Checked against: 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: 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%.
This calculator includes 3 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.