A tile order that falls short can hold up a bathroom, kitchen or hallway just when the fitting is underway. Ordering far too much is no better, particularly with premium porcelain or patterned tiles. Knowing how to calculate tile quantity accurately means measuring the area, accounting for the tile layout and checking exactly how the product is sold.
The basic calculation is straightforward, but the allowance for cuts and waste depends on the room, tile size and pattern. This guide explains how to work out what you need before placing an order.
How to calculate tile quantity for floors and walls
Start by measuring the surface to be tiled in metres. For a rectangular floor or wall, multiply the length by the width to find the area in square metres.
Length (m) x width (m) = area in m²
For example, a bathroom floor measuring 2.4m long by 1.8m wide is:
2.4m x 1.8m = 4.32m²
That is the net tiled area before allowing for cuts, breakages and spare tiles. The same method works for a wall. A kitchen splashback 3m wide and 0.6m high has an area of 1.8m².
Measure each floor or wall separately, even where rooms appear similar. A small difference around a doorway, chimney breast or boxing can change the quantity required. Record all measurements in metres to avoid mixing units.
Subtracting doors, windows and fixed openings
On a wall, it is usually sensible to deduct large openings such as doors, windows and full-height fitted units. Measure the opening and subtract its area from the total wall area.
For instance, a wall measuring 6m² with a window of 1.2m² leaves 4.8m² to tile. However, do not get too precise with small openings, sockets or narrow gaps. The cuts around them still use material, and any saving is often cancelled out by the extra wastage they create.
On floors, areas beneath permanent kitchen units, fitted furniture or a bath may not need tiling. This depends on the installation method and future plans. Tiling beneath removable appliances and freestanding furniture is generally worthwhile, but there is little point buying tiles for areas that will never be visible or accessible.
Add an allowance for cuts and waste
The net area is not the amount you should order. Every project needs an allowance for cutting tiles at edges, around pipes and corners, and for the occasional breakage during fitting.
For a simple square or rectangular room with tiles laid straight, allow 10% extra. This suits many standard bathrooms, kitchens and utility rooms.
Increase the allowance to 15% where the room has several corners, doorways, alcoves, pipework or awkward angles. Larger format tiles can also need a little more material in rooms that are not square, as offcuts are less likely to be reused.
Allow 15% to 20% for diagonal layouts, herringbone, chevron, brick-bond patterns with significant offsets, or detailed Victorian-style designs. These layouts create more edge cuts and require careful setting out. A patterned floor may also need additional tiles to maintain the design at thresholds and borders.
Using the 4.32m² bathroom floor example, a 10% allowance gives:
4.32m² x 1.10 = 4.75m²
You would therefore order at least 4.75m², then round up to the nearest full pack. Never round down simply because the calculation is close. Tiles are supplied in packs, and one extra pack is preferable to discovering that a discontinued batch is needed to finish the job.
Check how the tiles are sold
Tiles may be sold by the square metre, by the box, or occasionally by individual tile. The product information should state the coverage per pack. Divide your final quantity, including waste, by the pack coverage and round up.
If the chosen tile covers 1.08m² per pack and you need 4.75m²:
4.75m² ÷ 1.08m² = 4.4 packs
As partial boxes are not normally available, order five packs. Five packs provide 5.4m², giving a practical margin for cuts and a small number of future repairs.
Do not estimate from the number of tiles in a box alone. Tile sizes may include spacing tolerances, and the stated square metre coverage is the reliable figure to use. Check whether the coverage is based on the nominal tile size and whether grout joints are already allowed for in the manufacturer’s calculation.
Calculating individual tile quantities
Where tiles are sold individually, work out the area of one tile first. Convert millimetres to metres before calculating.
A 600mm x 300mm tile is 0.6m x 0.3m, so each tile covers 0.18m². Divide the final tiled area by 0.18m², then round up to a whole tile.
For a 4.75m² requirement:
4.75m² ÷ 0.18m² = 26.4 tiles
You would need at least 27 tiles, although it is wise to increase this for a cut-heavy layout. For mosaics, use the coverage stated for each sheet or box rather than trying to calculate from the individual pieces.
Measuring irregular rooms and shaped areas
Not every room is a neat rectangle. L-shaped kitchens, bay windows, shower enclosures and hearths need to be broken into smaller, manageable shapes.
Measure each rectangular section separately, calculate its area, and add the figures together. For a triangular section, multiply the base by the height and divide by two. This approach is more dependable than measuring the longest and widest points of an irregular room, which can lead to a substantial over-order.
Take particular care with curved walls and wet rooms. In these cases, a simple area calculation is still a useful starting point, but the number of cuts may be high. Allow extra material and discuss the layout with an experienced tiler before ordering, especially if using large porcelain slabs or a directional patterned tile.
Tile size, layout and batch considerations
The tile format affects both the quantity and the fitting process. Small tiles can follow uneven walls and curves more easily, while large-format tiles produce fewer grout lines but can generate larger offcuts. A straight lay usually gives the best material efficiency. Diagonal and herringbone designs look effective, but their increased waste allowance should be planned into the budget from the outset.
Before ordering, decide where full tiles will sit. A centred layout may leave balanced cuts at both sides of a wall, while starting from one edge can leave a narrow, awkward strip at the other. Good setting out often improves the finished appearance and can reduce unnecessary waste.
It is also good practice to buy all tiles for one area at the same time. Natural variation is part of many ceramic, porcelain and stone-effect ranges, and production batches can vary slightly in shade or pattern. Keep a few spare tiles from the same batch in a safe place for future repairs.
Do not forget trims, adhesive and grout
Tile quantity is only one part of the order. Measure exposed tile edges for trims, allowing for mitres and offcuts. Check the adhesive coverage against the tile size, substrate and trowel notch being used. Large-format porcelain, outdoor tiles and uneven backgrounds may require a different adhesive system and application method from a small ceramic wall tile.
Grout coverage depends on tile dimensions, joint width and tile thickness, so use the manufacturer’s coverage guidance rather than guessing. Floors in bathrooms, showers and wet areas also need appropriate preparation, including tanking, uncoupling or levelling products where required.
If you are unsure about an unusual layout, bring a sketch with your measurements to a showroom. The team at Caversham Tiles & Altwood Tiles can help check the quantities, pack coverage and fitting materials before work begins. A few minutes spent confirming the calculation can save a delayed installation, mismatched replacement tiles and an unnecessary second order.