Tile Quantity Calculator for Walls and Floors

How the calculation works

How to calculate tile quantity

Buying too few tiles is one of the most expensive mistakes in a tiling job. A dye lot can change, a finish can be discontinued, and a replacement box may not match the tiles already on the wall. Getting the count right the first time avoids that problem.

The formula and what it hides

The base logic is simple. Divide the area to be tiled by the area of one tile, then round up. For a 2 m × 3 m bathroom floor (6 m²) with 30 × 60 cm tiles (0.18 m² each), the bare count is 6 ÷ 0.18 = 33.3, which rounds up to 34 tiles before any allowance.

The calculator multiplies the area by (1 + waste ÷ 100) before dividing. The waste allowance covers the parts you cannot use: cuts at walls and corners, cuts around pipes, drains and sockets, and tiles broken during handling or fitting. Each cut usually wastes at least half a tile, and a room with many cuts uses more of the allowance than a simple rectangle would.

The formula assumes one tile size and one layout across the whole area. If you combine two formats, or tile a floor and a wall with different tiles, calculate each area separately and add the results.

Tile formats and how they change the count

Tile size changes the count more than most people expect. A 30 × 60 cm tile covers 0.18 m², so about 5.6 tiles are needed per square metre. A 20 × 20 cm mosaic covers 0.04 m², so 25 are needed per square metre. The same wall needs roughly 4.5 times as many mosaic pieces.

Common formats include 20 × 20 cm, 30 × 60 cm, 60 × 60 cm and 60 × 120 cm. Large formats mean fewer grout lines, which many people find easier to keep clean in bathrooms and kitchens. They also demand more care during fitting. Any unevenness in the substrate shows up more clearly on a large tile, so check the flatness of the surface before the first tile goes on, and ask the tiler whether the substrate needs levelling.

Layout and the waste allowance

The layout decides how much of each tile is cut away. A straight layout, with joints parallel to the walls, produces the fewest cuts. A diagonal layout at 45 degrees produces many triangular offcuts, so it needs a larger allowance. Complex patterns such as herringbone, or a border of mosaic, need more again.

Instead of applying a fixed percentage out of habit, ask your tiler which allowance they use for the layout you have chosen, then test a few values in the calculator to see how the count changes. A higher allowance costs a little more in material, while a shortfall can stop the job.

Standards and tile classification

The European product standard for ceramic tiles, EN 14411, defines tile types, classification, characteristics and marking. It does not set a waste allowance, which is a matter for the installer and the designer. Under EN 14411, porcelain stoneware with water absorption of 0.5% or less falls in Group BIa. Low absorption matters for wet areas and external floors, where moisture is constant and the tile must not soak it up. Slip resistance is a separate rating, which the manufacturer should state on the datasheet.

A worked example in a Singapore flat

In a 4-room HDB flat in Tampines, retiling a toilet is a common renovation job. Suppose the floor is 1.5 m × 2.0 m and the walls are 2.4 m high. The floor is 3.0 m². The walls around the perimeter total 2 × (1.5 + 2.0) × 2.4 = 16.8 m², with the door not deducted. The total area is 19.8 m². With 30 × 60 cm tiles and a 10% allowance, the count is 19.8 × 1.10 ÷ 0.18 = 121 tiles.

Renovation work changes the surface first. Old tiles are hacked off before new ones go on, and the cleared wall can differ from the original drawings, with uneven plaster or a different wall line. Measure the bare surface, not the old tiles, before you calculate. The same method applies to a condominium in Bukit Timah or a landed house in Bishan.

When to use this calculator

Use it for rectangular walls and floors with one tile size and one layout. It suits bathroom walls, kitchen backsplashes, and floors in homes, shops and offices, where the cut pattern is predictable.

When not to use it

Do not rely on the calculator alone for two tile sizes in one area, a border or feature strip, a pattern with a repeat, or irregular shapes such as niches, curved walls, vanities with cut-outs or sloped ceilings. A percentage cannot capture the cuts in these areas, and a tiler can plan them more precisely.

Common mistakes

Buying exactly the calculated number. This is the most common and most expensive error. A tile can break in transit, a cut can fail, and a colour can be discontinued. A few extra tiles from the same batch usually cost less than the trouble of a mismatch.

Measuring the wrong area. In a bathroom, people often forget the strip behind the toilet bowl, the wall above a recessed basin, or the area above a false ceiling where tiling continues. Measure wall to wall and floor to ceiling. Deduct only openings wider than 1.5 m. Small windows and niches stay in the calculation, because the cuts around them use up material anyway.

Forgetting the box. Tiles are sold by the box, so the result must be rounded up to a whole number of boxes. A calculation that ends at 121 tiles still needs the box count from the packaging.

Using the same allowance for every layout. A straight layout and a diagonal one need different allowances. Changing the layout without changing the allowance is a common cause of running short.

Working with a professional

For a standard bathroom or kitchen, the calculator is enough. Speak to your tiler before buying if you plan to combine two formats, use a herringbone or other pattern, or have irregular cuts such as columns, curved niches or countertops with cut-outs. An experienced tiler can plan the cuts to reduce waste, which matters most with expensive tiles, where each piece carries real weight in the budget.

For larger renovation works, a main contractor or interior designer can check the quantities against the drawings before you place the order. For technical questions on tiling and building works, start with the Building and Construction Authority.