How many tiles do I need? Waste, cuts and boxes explained
6 min read · Updated 2026-10-12 · BuildCalc
Dividing the area to be tiled by the area of one tile gives the theoretical minimum, and it is almost always the wrong number to buy. Tiles get cut at the edges of a room, patterns and diagonals waste more, and a broken tile mid-job means a trip to the shop — where the batch may have sold out and the shade may not match. Here is how to size the order properly.
Working out the theoretical count
Measure the area to be covered and divide by the area of a single tile. A twelve-inch tile covers one square foot, so a hundred-square-foot floor needs a hundred tiles at minimum; a six-inch tile covers a quarter of a square foot, so the same floor needs four hundred. Wall tiling works the same way, though you can often deduct the area of a bath or shower screen.
Keep the units consistent. Tile sizes are usually quoted in inches or centimetres, areas in square feet or square metres, and mixing them is the fastest way to order ten times too many. Convert everything to one unit before dividing.
Why you always add waste
Tiles along the edge of a room are cut, and the offcut is usually too small to use anywhere else. A simple grid in a rectangular room wastes the least, around ten per cent. Diagonal layouts, herringbone patterns, borders and rooms full of doorways, pipes and alcoves waste considerably more, so fifteen to twenty per cent is the sensible allowance.
Large-format tiles need their own thinking. Each one covers more area, so a single break costs more, and they are more likely to chip when cut. They also look best with fewer cuts, which usually means planning the layout from the centre of the room outward — a decision that changes how many tiles are consumed, not just how they look.
Buying by the box, and keeping spares
Tiles are sold in boxes containing a stated area, and you can only buy whole boxes. Divide your area-plus-waste by the coverage per box and round up. It is worth checking whether a part-box is available as a single, since that can save a whole box on a small job.
Keep any spares. Tiles are fired in batches that vary subtly in shade, so a replacement bought a year later may not match, and a chipped tile in a bathroom is impossible to disguise. One spare box in the garage is insurance against both.
Run your own numbers
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Common questions
How much waste should I allow for tiles?
About ten per cent for a simple square layout in a rectangular room, fifteen to twenty per cent for diagonal patterns, large tiles or rooms with many cuts.
Do I need the same tiles as spares?
Yes, and from the same batch. Shade varies between production runs, so a later purchase may not match what is already on the floor.
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