Tile Calculator m²: Tiles, Boxes and Grout Bags

Estimate only. Check product labels and the building rules in your state or territory before you buy or build.

Quick answer

Divide the area by the space one tile takes up with its grout joint, add a waste allowance and round up. A 3 × 2.5 m floor is 7.5 m², and a 300 × 600 mm tile with a 3 mm joint takes up 303 × 603 mm, or 0.1827 m², so 41.0 tiles cover the floor. With 10% extra for cuts you buy 46 tiles, which is 7 boxes of 1.26 m².

How to use the tile calculator

Choose Room size and enter the length and width in metres. For an L-shaped room, split it into rectangles and add each one as another area. If you already know the floor area in m², choose Total area.
Pick a tile size from the list, or choose Other size and type the size on the carton. Then enter the grout joint and pick the layout.
Open Box size and waste to enter the coverage per carton in m², or switch to Tiles and enter the number of tiles per carton. The waste allowance follows the layout; change it if your tiler uses a different figure.
For grout, enter the tile thickness and pick the bag size. The density and the 15% wastage allowance are under Grout density and extra.

How do you calculate how many tiles you need per m²?

Each tile takes up its own size plus one joint width in each direction, so a 300 × 600 mm tile with a 3 mm joint fills a 303 × 603 mm patch of floor, which is 0.1827 m². Divide the area by that patch, add a waste allowance for cuts and breakages, and round up to whole tiles. For boxes, the face area of those tiles is divided by the m² printed on the carton.

Grout fills the joints, so the amount depends on how much joint there is per m² and how deep it is. Grout makers print the formula below on their data sheets, with the joint depth equal to the tile thickness. A density of 2.0 reproduces most of the coverage table on the ARDEX FG 8 data sheet, for example 0.6 kg/m² for 50 × 50 × 5 mm tiles and 0.1 kg/m² for 600 × 600 × 10 mm tiles, both with 1.5 mm joints.

area = length × width, added up for each rectanglespace per tile = (tile length + joint) × (tile width + joint)tiles = area ÷ space per tiletiles to buy = tiles × (1 + waste % ÷ 100), rounded upboxes = tiles to buy × tile face area ÷ m² per carton, rounded upgrout in kg/m² = (L + W) ÷ (L × W) × joint width × joint depth × density, all lengths in mm

How many tiles and how much grout per m²?

Computed with the formulas above for 3 mm joints, the minimum for pressed-edge tiles, and a grout density of 2.0. Tiles are taken as 8 mm thick, except 100 × 100 mm at 5 mm and 600 × 600 mm at 10 mm, the depths in the ARDEX FG 8 table.

Tiles and grout per m² by tile size, 3 mm joints
Tile size	Tiles per m²	Tiles for 10 m² with 10% extra	Grout per m²
100 × 100 mm	94.26	1,037	0.60 kg
300 × 300 mm	10.89	120	0.32 kg
450 × 450 mm	4.87	54	0.21 kg
300 × 600 mm	5.47	61	0.24 kg
600 × 600 mm	2.75	31	0.20 kg
150 × 900 mm	7.24	80	0.37 kg

Grout weights are before the wastage allowance. ARDEX’s own table gives 0.23 kg/m² for 600 × 600 × 10 mm tiles with 3 mm joints, a little more than the formula.

Worked examples

300 × 600 mm tiles on a 3 × 2.5 m bathroom floor

The floor is 3 × 2.5 = 7.5 m². With 3 mm joints each tile takes up 303 × 603 mm, which is 0.1827 m², so 41.0 tiles cover the floor and 42 whole tiles is the minimum. A straight layout with 10% extra gives 46 tiles. Their face area is 46 × 0.18 = 8.28 m², so with cartons of 1.26 m² you need 7 boxes, which hold 8.82 m².

For 8 mm thick tiles and a grout density of 2.0, the joints take 0.24 kg of grout per m², 1.80 kg for the floor. With 15% for wastage that is 2.07 kg: one 5 kg bag, or two 1.5 kg bags.

600 × 600 mm rectified tiles in an L-shaped living area

Split the L into two rectangles, 5 × 4 m and 2 × 1.5 m, which add up to 20 + 3 = 23 m². Enter them as Area 1 and Area 2. With 2 mm joints each tile takes up 0.3624 m², so 63.5 tiles cover the floor, and a straight layout with 10% extra gives 70 tiles. If the carton holds 1.44 m² (four tiles), that is 18 boxes.

With rectified tiles selected under Grout joint check, 2 mm meets the 1.5 mm minimum; pressed-edge tiles would need 3 mm. For 10 mm thick tiles the grout comes to 0.13 kg per m², or 3.53 kg with 15% for wastage, so one 5 kg bag.

What grout joint width do rectified and pressed tiles need?

At least 1.5 mm for rectified tiles and 3 mm for pressed-edge tiles, and no wider than 5 mm, according to Johnson Tiles. Johnson Tiles describes rectified edges as clean edges for a closer look, and pressed-edge tiles as having wider joints and rounder corners. Pick rectified or pressed-edge under Grout joint check and the calculator tests your joint against that minimum and against the 5 mm maximum.

The grout sets limits too: ARDEX FG 8 is made for joints from 1 mm to 8 mm wide. Where your tile maker gives a different joint for its product, its instructions come first.

How do I use the m² per carton?

Enter it as the coverage per box, and the calculator divides the face area of the tiles you buy by it. Johnson Tiles labels a 300 × 600 × 8 mm floor tile “1 Ctn = 1.260 SQM” with 7 tiles per carton, which is exactly 7 × 0.3 × 0.6 m: the face area of the tiles, without joints.

Seven of those cartons hold 49 tiles and 8.82 m² of tile face, enough for the 46 tiles the first example needs. If the carton gives a tile count instead, switch Box label gives to Tiles and enter the count.

Cartons differ between products, even at the same tile size. Johnson Tiles sells one 600 × 600 mm floor tile in cartons of 4 tiles (1.44 m², 9 mm thick) and another in cartons of 3 tiles (1.08 m², 9.5 mm thick). The calculator keeps the 1.26 m² when you pick another size from the list, so replace it with the figure on your carton.

Common questions

How many tiles do I need per square metre?

With 3 mm joints you need 5.47 tiles of 300 × 600 mm per m², 2.75 of 600 × 600 mm, 4.87 of 450 × 450 mm and 10.89 of 300 × 300 mm. The joint adds to the space each tile takes up, so these counts are slightly lower than 1 m² divided by the tile’s face area. Multiply by your floor area, add the waste allowance and round up.

How many boxes of tiles do I need for 10 m²?

You need 9 cartons of 300 × 600 mm tiles at 1.26 m² per carton for 10 m² with 3 mm joints and 10% extra. That is 61 tiles with a face area of 10.98 m², and 10.98 ÷ 1.26 rounds up to 9. Check the m² or tile count on your own carton, because it varies by product.

How much extra tile should I allow?

Allow an extra 10% for cuts and wastage, the figure Johnson Tiles gives for working out how many tiles you need. The calculator starts diagonal layouts at 15% and herringbone at 20% because nearly every edge tile is cut; these are planning figures, not a standard. Johnson Tiles also suggests keeping some extra tiles on hand in case you need to replace one later.

How much grout do I need per m²?

About 0.24 kg per m² for 300 × 600 mm tiles 8 mm thick with 3 mm joints, at a grout density of 2.0. Small tiles need much more: ARDEX’s FG 8 data sheet gives 1.2 kg/m² for 50 × 50 × 5 mm mosaics with 3 mm joints and 0.6 kg/m² for 100 × 100 × 5 mm tiles. Add 15 to 20% for wastage on top.

What grout joint should I use for 600 × 600 tiles?

Use at least 1.5 mm if the tiles are rectified and 3 mm if they are pressed-edge, and no more than 5 mm, as Johnson Tiles recommends. A 2 mm joint on 600 × 600 mm rectified tiles takes about 0.13 kg of grout per m² at 10 mm deep; a 3 mm joint takes 0.20 kg. Check the product’s own installation notes first.

Why add 15% to the grout?

Because the grout maker says to: the ARDEX FG 8 data sheet says to allow an additional 15 to 20% for wastage, and the calculator starts at 15%. The same sheet notes that coverage varies with tile size, joint width and depth, the method of application and site conditions. For the 3 × 2.5 m floor in the first example, 15% turns 1.80 kg into 2.07 kg, still one 5 kg bag.

Sources

Johnson Tiles, FAQs (checked 19 October 2026)Allow an extra 10% for cuts and wastage; grout joints of at least 1.5 mm for rectified and 3 mm for pressed tiles, not wider than 5 mm.
Johnson Tiles, Carrara Statuari Platinum Lappato Tiles 300x600 (checked 19 October 2026)300 × 600 × 8 mm; 1 carton = 1.260 m², 7 pieces per carton.
Johnson Tiles, Caspian Beige Matt Tiles 600x600 (checked 19 October 2026)600 × 600 × 9 mm; 1 carton = 1.440 m², 4 pieces per carton.
Johnson Tiles, Lorimer Iron Structured Tiles 600x600 (checked 19 October 2026)600 × 600 × 9.5 mm; 1 carton = 1.080 m², 3 pieces per carton.
Johnson Tiles, Floor tiles (checked 19 October 2026)Floor tile formats including 300 × 300, 450 × 450, 300 × 600, 600 × 600 and 150 × 900 mm.
ARDEX Australia, ARDEX FG 8 (checked 19 October 2026)1.5, 5 and 20 kg packs; tile joints 1 to 8 mm wide.
ARDEX Australia, ARDEX FG 8 data sheet (checked 19 October 2026)Coverage table in kg/m² by tile size, depth and joint width; allow an additional 15 to 20% for wastage.
Cégécol (Sika France), CARROJOINT PREMIUM data sheet (checked 19 October 2026)Grout consumption formula (L + l) × joint width × depth × density ÷ (L × l).

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