How Many Tiles Do You Need? Tile Quantity Calculator

How the calculation works

How to work out how many tiles you need

Tiling calculations start from a simple division. You divide the area to be covered by the area of one tile, then round the result up to a whole number. A bathroom floor measuring 2 m × 3 m has an area of 6 m². With 30 × 60 cm tiles, each covering 0.18 m², that is 6 ÷ 0.18 = 33.3, which rounds up to 34 tiles before any allowance is added.

The division alone is never enough. Almost every tiled area involves cuts: at the corners, along the skirting, around sockets, around the waste pipe and the cistern, and at the edges of an inspection cover. Each cut leaves an offcut that usually cannot be reused. The waste allowance covers these cuts, the tiles broken during fitting, and a small reserve for repairs later.

Applying a 10% allowance to the same floor gives 6 × 1.10 ÷ 0.18 = 36.7, which rounds up to 37 tiles. The calculator applies exactly this rule: the area multiplied by one plus the allowance, divided by the area of one tile, rounded up. Because the result is always rounded up and never down, the figure is the minimum for the chosen layout.

Why the allowance depends on the layout

The allowance is not a fixed property of the tile. It depends on how the tiles are laid. A straight lay, where the joints run parallel to the walls, produces the fewest cuts. A diagonal lay at 45 degrees produces many more cuts along every edge, because every perimeter tile is cut at an angle. Complex patterns such as herringbone, or a mix of two formats, produce the most cuts and the most offcuts that cannot be reused.

For this reason, the calculator asks for the allowance rather than assuming one. Choose the figure that matches the layout you intend to use. If you switch from a straight lay to a diagonal one after buying, the material you have may fall short, and the tiles from the same production batch may no longer be available.

It helps to know what the standard does and does not cover. EN 14411:2016 covers the definitions, classification, characteristics and marking of ceramic tiles. It tells you what a tile is and how it is classified, but it does not say how many tiles to buy. That judgement sits with the person laying the tiles, and the waste allowance is the place where it is made.

Tile sizes and what they mean for the count

The tile size controls the number of pieces, the number of grout lines and the amount of cutting. Four formats cover most domestic work:

• 20 × 20 cm (0.04 m² per tile, 25 tiles per m²): the traditional bathroom and small-wall format. Small tiles need more grout lines, but they follow curves and slightly uneven surfaces easily.
• 30 × 60 cm (0.18 m² per tile, about 5.6 tiles per m²): a common middle-sized format that balances the number of cuts against the look of the finished wall.
• 60 × 60 cm (0.36 m² per tile, about 2.8 tiles per m²): a standard choice for floors in wet areas and for open-plan kitchens.
• 60 × 120 cm (0.72 m² per tile, about 1.4 tiles per m²): large format, with fewer grout lines, which makes cleaning easier.

Fewer grout lines are an advantage in rooms that need regular cleaning, such as bathrooms and kitchens. Large tiles are less forgiving, though. Any unevenness in the substrate shows more on a large tile, and a surface that is out of flat can cause lippage, where one tile stands proud of its neighbour, or cracking under load. Check the flatness of the substrate before ordering, and follow the tile manufacturer's guidance on the flatness required and on the adhesive to use.

Choosing a tile range

The calculator gives you a quantity without needing a price. If you also want an estimate of the material cost, enter the price per square metre of the tile you are considering, taken from a supplier quote or the shelf label. Tile ranges fall into three broad groups:

• Economy: standard-series ceramic and factory seconds, suited to low-traffic areas and tightly controlled budgets. Check seconds carefully for shade and size variation before buying, because they can differ from first-grade product.
• Mid-range: established manufacturers with standard formats such as 30 × 60 cm and 60 × 60 cm, offering a good balance between durability and finish.
• Premium: large formats of 60 × 120 cm and above, special effects such as marble or timber looks, and design-led ranges from manufacturers abroad.

Tiles are widely sold through large DIY retailers and builders' providers, so it is worth comparing a few ranges before settling on one format. Whatever the range, buy the full quantity in a single purchase. Tiles with the same product code can vary slightly in shade between production batches, and a patch repaired with a different batch is easy to spot.

Tile adhesive and grout are separate quantities. Work them out from the coverage given on each product's packaging or technical data sheet, because coverage depends on the trowel size, the substrate and the tile format. The calculator covers the tiles only.

Common mistakes

Ordering the exact figure. This is the most expensive mistake, because a product line can run out, change batch or leave the catalogue between the first purchase and a later repair. A little spare material is usually worth having, and it costs far less than a mismatched patch.

Missing parts of the area. In bathrooms it is easy to forget the wall behind the toilet, the area above a recessed basin and the strip above a suspended ceiling. Measure wall to wall, from the floor to the ceiling or to the point where the tiling will finish.

Deducting the wrong openings. Only openings wider than 1.5 m are worth deducting. Small windows and niches are not worth deducting, because the cuts around them use up tile anyway.

Changing the layout without changing the allowance. Laying diagonally increases the number of cuts noticeably. Switching to a diagonal layout while keeping the allowance for a straight lay is a common reason for a shortfall.

Entering the tile size in the wrong unit. The calculator takes tile dimensions in centimetres and areas in metres. Enter 30 and 60 for a 30 × 60 cm tile, not 300 and 600, which would be a millimetre figure.

When to ask a tiler

For a standard wall or floor in one tile size, the calculator is enough. Ask a tiler before ordering when you are combining two formats in the same area, when the pattern is herringbone or another complex layout, or when the room has many irregular cuts, such as columns, curved niches or worktops with angles. An experienced tiler can plan the cuts to reduce waste, which matters most when the tile is expensive and every piece carries real value.

The calculator assumes one rectangular area and one tile size. For a room with several separate areas, run the calculator for each area and add the results together, bearing in mind that each result is rounded up on its own.

Units and measuring

The calculator uses metric measurements: metres for the area and centimetres for the tile. If a plan or an older measurement is in feet, convert it to metres first, since 1 ft is 0.3048 m. Measure wall to wall and floor to ceiling, and take each measurement twice before you write it down. Check the final figure against the coverage on the product data sheet and the number of tiles in each box before placing the order.