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How many tiles go on a square metre?

Divide 1 m² by the tile's area including the grout joint: a 30 × 60 cm tile with a 3 mm joint takes up 0.1827 m², so 5.5 tiles fit a square metre.

The formula — and why the grout joint has to be included

A tile doesn't cover only its own footprint on the wall. It covers its footprint plus half the joint all the way round — which works out to a full joint width in each direction once you're counting across many tiles. The correct calculation is therefore:

Tiles per m² = 1 ÷ ((w + j) × (l + j)), where w is the tile's width in metres, l is the tile's length in metres, and j is the grout joint width in metres (3 mm = 0.003 m).

Example: A 30 × 60 cm tile with a 3 mm joint. (0.30 + 0.003) × (0.60 + 0.003) = 0.303 × 0.603 = 0.18271 m². 1 ÷ 0.18271 = 5.47 tiles per m², so 5.5.

For comparison, without a joint: 0.30 × 0.60 = 0.18 m² → 5.56 tiles per m². The difference is 1.6%. That sounds like nothing, but over 30 m² of tiled surface it's about 0.5 m² — and you might not save a whole box, but you avoid ordering one too many once wastage is added on top.

Common sizes with a 3 mm grout joint

Here's the tile count per m² for the usual sizes, calculated with a 3 mm joint (rounded):

• 10 × 10 cm: about 94 tiles per m².
• 15 × 15 cm: about 43 tiles per m².
• 20 × 20 cm: about 24 tiles per m².
• 20 × 25 cm: about 19 tiles per m².
• 30 × 30 cm: about 11 tiles per m².
• 30 × 60 cm: about 5.5 tiles per m².
• 40 × 40 cm: about 6.2 tiles per m².
• 60 × 60 cm: about 2.8 tiles per m².
• 60 × 120 cm: about 1.4 tiles per m².
• Metro tiles 7.5 × 15 cm: about 84 tiles per m².

Note that the box label almost always states how many m² the box covers. That figure takes priority over your own calculation, because the manufacturer knows the tile's actual calibrated size — a "30 × 60" is rarely exactly 300.0 × 600.0 mm.

The grout width changes the number more than you'd think

The smaller the tile, the more the joint matters. A 10 × 10 cm tile has just as much joint per square metre as a 60 × 60 cm tile has over six square metres.

Example with 10 × 10 cm:

• 2 mm joint: (0.102 × 0.102) = 0.010404 m² → 96 tiles per m².
• 3 mm joint: (0.103 × 0.103) = 0.010609 m² → 94 tiles per m².
• 5 mm joint: (0.105 × 0.105) = 0.011025 m² → 91 tiles per m².

So going from 2 mm to 5 mm loses 5 tiles per m² — about 5%. Decide on the joint width before you order, not once the tiler's bucket is standing in the hallway.

Typical joint widths: 2-3 mm for calibrated wall tiles, 3-5 mm for floor tiles, 5-10 mm for unglazed or handmade tiles with an uneven edge, and 10-15 mm for outdoor paving, where movement needs to be absorbed. The supplier's own instructions set the final figure — some tiles specify a minimum joint precisely because their sizes vary.

From tiles per m² to total tiles

Tiles per m² is only half the job. The full calculation runs:

1. Find the area. Floor = length × width, measured internally. Wall = the room's internal perimeter × the tiled height.
2. Add wastage. 10% for a straight lay, 15% for offset or diagonal, 15-20% for large format above 60 × 60 cm.
3. Multiply by tiles per m² to get the count.
4. Round up to whole boxes.

Example: A bathroom is 2.40 × 3.00 m, and the walls are to be tiled with 30 × 60 cm tiles up to 2.20 m. Perimeter = 2 × (2.40 + 3.00) = 10.80 m. Wall area = 10.80 × 2.20 = 23.76 m². 10% wastage: 23.76 × 1.10 = 26.14 m². Tiles: 26.14 × 5.47 = 143 tiles. If a box holds 6 tiles (1.08 m²): 143 ÷ 6 = 23.8 → 24 boxes.

How much grout and adhesive do you need?

Grout consumption follows directly from tile size and joint width — small tiles mean more grout. Rough figures, but the manufacturer's numbers on the bag take priority:

• Small tiles (10 × 10 cm), 3 mm joint: about 0.8-1.2 kg of grout per m².
• 30 × 60 cm, 3 mm joint: about 0.3-0.5 kg of grout per m².
• 60 × 60 cm, 3 mm joint: about 0.2-0.4 kg of grout per m².
• Tile adhesive: about 3-5 kg per m² with a 6 mm notched trowel, and about 5-8 kg per m² with a 10 mm one — large tiles need the bigger notch.

Joint depth matters too: a 10 mm thick paver has twice the grout volume per linear metre of a 5 mm wall tile at the same joint width.

What the number doesn't tell you

Tiles per m² says nothing about how many tiles need cutting. That's decided by how the pattern is set out relative to the walls, and it's often the biggest source of surprises. If the first row is set so the last row ends up 2 cm wide, every single tile in that row has to be cut, and they often chip. So work out in advance how many whole tiles fit on each wall, and shift the layout so the first and last rows come out equal in width and at least about a third of a tile wide.

Example: The wall is 3.00 m wide, the tile is 30 cm + 3 mm joint = 30.3 cm. 300 ÷ 30.3 = 9.90 tiles. The last tile ends up 0.90 × 30.3 = 27 cm — perfectly fine. If the wall were 2.75 m: 275 ÷ 30.3 = 9.08, giving a last tile of only 2.4 cm. Instead, trim about 14 cm off both the first and last tile, so both edges match.

That calculation needs you to know the wall's precise internal length and height. If you have a measured floor plan of the room, the wall lengths are already there — and HouseSense also shows every wall as an elevation, the wall seen from the front with its height and its door and window openings placed to scale, which is exactly the view a tile layout needs to be planned on.