Tile Quantity Calculator for Floors and Walls

How the calculation works

How to work out how many tiles you need

Ordering too few tiles is one of the most common and expensive problems in a tiling job. A batch can vary in colour from the next, and a discontinued line may not be available when you return for a replacement. This calculator divides the area you want to cover by the area of one tile, adds a waste allowance for cuts and breakages, and rounds the result up to a whole tile.

The formula and what it leaves out

Length times width gives the area in square metres. The factor (1 + D/100) adds the waste allowance. Dividing by the area of one tile gives the number of tiles, and the ceiling function rounds up to the next whole tile, so the count never comes out below the exact figure.

The formula assumes that every tile can be used in full, which is never quite true. Every cut leaves an offcut, and offcuts from one wall edge are not always useful elsewhere in the room. The allowance covers that loss, the breakages that happen during laying and a small reserve for future repairs. The formula does not see window reveals, recessed niches or a floor waste, so the result is only as good as the area you enter.

Check the actual size of the tile on the packaging or the data sheet. Some tiles are sold as rectified, and their stated size is the finished size. The calculator uses whatever figures you enter, so a wrong tile size gives a wrong count with no warning.

Tile sizes and their effect on the count

The size of the tile changes the number of pieces and the look of the finished room. Four formats cover most jobs:

• 20 × 20 cm (0.04 m² per tile, 25 per m²): the classic size for bathroom floors and small wall areas, and a common size for mosaic sheets.
• 30 × 60 cm (0.18 m² per tile, about 5.6 per m²): a common mid-size format for walls and floors that balances the number of cuts against the visual effect.
• 60 × 60 cm (0.36 m² per tile, about 2.8 per m²): a common floor size in kitchens and open-plan living areas.
• 60 × 120 cm (0.72 m² per tile, about 1.4 per m²): a large format with fewer grout lines, which makes cleaning easier, but it needs a flatter surface and more careful handling.

Large tiles show every irregularity in the surface beneath them. Check the substrate tolerance in the manufacturer's data sheet and have the surface levelled before tiling, rather than relying on the adhesive to make up the difference. Heavy tiles also need proper handling on site, so plan the delivery and the lifting in advance.

Waste allowance by layout

The allowance depends on how the tiles are set out:

• Straight lay, with grout lines parallel to the walls: 10%
• Diagonal lay at 45 degrees: 15%
• Complex patterns such as herringbone or stacked mosaic: 20% or more

These are common working allowances, not a published standard. EN 14411 classifies ceramic tiles by their properties, but it does not set a waste allowance, which is left to the person laying the tiles. If your layout is unusual, ask your tiler what allowance they would use.

Take a 3 m × 2.5 m bathroom wall tiled with 60 × 60 cm tiles on the diagonal. The area is 7.5 m². With a 15% allowance the calculation is 7.5 × 1.15 ÷ 0.36 = 23.96, so you need 24 tiles. A straight lay with a 10% allowance would need 7.5 × 1.1 ÷ 0.36 = 22.9, which rounds up to 23 tiles. Diagonal work with many cuts around a door frame or a recessed shelf can need more than the 15% allowance, so the choice of layout matters as much as the arithmetic.

Choosing the tile type

Tiles come in three broad tiers. The calculator does not price them, but the tier helps you decide how much to buy:

• Economy: standard glazed ceramic and seconds. Suitable for low-traffic walls and budget projects. Check the batch number on each box and buy a little more than the calculation shows.
• Mid-range: established ranges in common sizes such as 30 × 60 cm and 60 × 60 cm, with a reasonable balance of durability and finish.
• Premium: large formats (60 × 120 cm and above), printed stone or timber effects and designer ranges. These are the tiles where an extra piece costs most, so the layout plan matters more.

Ceramic and porcelain differ in water absorption. EN 14411 places porcelain in group BIa, which has water absorption of 0.5% or less. Porcelain is generally suited to wet areas and external floors, while standard glazed ceramic tiles are usually best for interior walls. For a bathroom floor, check the slip resistance rating against AS 4586, the Australian standard for the slip resistance of pedestrian surface materials, as well as the data sheet for the intended use.

Adhesive and grout are separate purchases. Their coverage depends on the tile size and the trowel notch, so use the figures on their own data sheets when you estimate how many bags to buy.

Common mistakes

Ordering exactly the calculated number. This is the most common and most expensive mistake. A product can be discontinued, change batch or sell out between the first purchase and a later repair. A few spare tiles kept in storage are often worth more than the cost of an extra box.

Measuring the wrong area. Measure wall to wall and floor to wall, and run the calculator once for each wall and for the floor. Adding the results is safer than working from one total area, because each rounding step adds to the total. Do not deduct small windows and niches, since cutting around them uses the material anyway. Deduct only large openings, such as a wide garage roller door.

Laying on the diagonal with the straight-lay allowance. Diagonal layouts increase the number of cuts considerably. Buying a 10% allowance for a diagonal lay often leaves you short by a box, and that box may not be from the same batch.

Forgetting the niches and the top of the wall. In bathrooms, people often leave out the area behind the toilet pan, the wall above a recessed vanity and the strip above a suspended ceiling. Leave out an area and the count comes up short, because those strips still need cut pieces.

Local standards and approvals

Tile products are classified under EN 14411, the European standard for ceramic tiles. Australian requirements apply to the building work around the tiles, including waterproofing in wet areas, which the National Construction Code (NCC) regulates. State and territory rules and local councils may add requirements, so check them before you start work. For structural questions, such as whether a floor can carry large-format tiles, speak to a licensed builder or a building surveyor.

When to ask a tiler first

For a standard floor or wall, the calculator is enough. Speak to a tiler before ordering when you combine two tile formats, use a herringbone or stacked pattern, or the room has irregular cuts. Columns, curved niches, benchtops with angled cut-outs and sunken baths all add cuts that the calculator cannot see. An experienced tiler can plan the cut positions to reduce waste, which matters most with expensive tiles.

When not to use this calculator

The calculator assumes rectangular tiles laid in a regular pattern. For hexagons, irregular shapes or mosaic sheets that need pattern matching, work out the area of one tile from the data sheet and draw the layout on a plan before ordering. The calculator also does not replace a measurement on site. Measure the room yourself, and check the dimensions against the plan before you buy.

Enter the area in metres and the tile size in centimetres, as the calculator's labels show. Metric units are used throughout, and the calculator gives the count as a whole number of tiles, which you can then convert into boxes using the number printed on the packaging.

For the rules that apply to tiled wet areas, check the National Construction Code and your state or territory building regulator, and speak to a licensed tradesperson before starting any wet area work.