Measuring the area correctly
Measure the longest length and the longest width of the area to be tiled and multiply them, rather than trying to measure every alcove and step separately. This slightly overstates the true area but builds in a natural first buffer against the inevitable odd shapes in a bathroom.
For walls, measure floor to ceiling (or floor to the agreed tiling height) and total wall length, then subtract door and window openings only if they are large enough to genuinely save tiles, such as a full bath panel void or a large window reveal. Small openings are rarely worth deducting once cutting and wastage are accounted for.
Always measure at the widest and tallest points of a room, not an average, because most rooms are not perfectly square and the largest dimension is what the tiling actually has to cover.
Wastage: why it is not just a fudge factor
Wastage covers cuts around fittings, breakages in handling, the tiles used to check pattern and colour before committing, and future replacements if a tile ever gets damaged. Ordering to the exact calculated area with no allowance is the single most common reason a job stalls waiting for a second delivery.
Wastage should be higher for smaller rooms (more cutting relative to floor area), irregular room shapes, diagonal or pattern lays, and larger-format tiles, where a single miscut wastes a proportionally bigger piece of material.
It should be lower for large, simple rectangular rooms tiled in a straight grid with small or mid-sized tiles, where cutting is a small proportion of the overall job.
Wastage percentages by scenario
There is no single wastage figure that suits every room. Use the scenario closest to your own job, and round up to the nearest full box.
| Scenario | Recommended wastage |
|---|---|
| Large rectangular room, straight lay, small/mid tile | 8-10% |
| Standard bathroom floor, straight lay | 10-12% |
| Small ensuite or cloakroom, multiple fittings to cut around | 15-20% |
| Large-format tile (600mm+), any room | 12-15% |
| Diagonal lay | 15-18% |
| Herringbone or chevron pattern | 15-20% |
| Natural stone with size/shade variation | 12-15% |
Worked example: a family bathroom floor
Room measures 2.4m by 1.9m at its widest points, giving a base area of 4.56 m2. This is a fairly standard rectangular family bathroom with a WC, basin pedestal and bath to cut around, tiled in a straight lay with a 300x300mm porcelain tile.
Applying a 12% wastage allowance (standard bathroom floor with a moderate amount of cutting) gives 4.56 x 1.12 = 5.11 m2. Rounding up to the nearest full box, if boxes cover 1.08 m2 each, that is five boxes (5.4 m2), giving a small genuine spare for future repairs.
Worked example: a kitchen splashback
A run of worktop is 3.6m long, with a 600mm upstand height, giving a base area of 2.16 m2, tiled in 100x200mm ceramic metro tile in a brick bond pattern around two double sockets.
Metro tile in brick bond with a modest number of socket cut-outs sits closer to the 12% to 15% band rather than the lowest wastage figure, because of the socket cuts and the number of end-of-row cuts a brick bond pattern generates. Applying 14% gives 2.16 x 1.14 = 2.46 m2, rounded up to whatever box size is supplied, typically meaning three or four boxes depending on the pack size.
Batch numbers and ordering sensibly
Always check that every box carries the same batch or shade number before tiling begins. Porcelain and ceramic tiles can vary slightly in shade between production batches, and mixing batches on a visible wall or floor is one of the most common and most avoidable complaints in tiling.
Where a job is likely to be phased, or where a small amount might be needed later for a repair, it is worth buying slightly over the calculated wastage and keeping a box or two in reserve, because the specific batch is very unlikely to still be available if you go back for more in a year's time.
For large or unusually shaped rooms, or where you are unsure which wastage percentage applies, our free survey includes an accurate tile take-off as standard, so you are not guessing before placing an order.
Frequently asked questions
What percentage wastage should I add for a standard bathroom?
Around 10% to 12% for a typical family bathroom floor in a straight lay is a sensible starting point, rising towards 15% to 20% for a small cloakroom with more fittings to cut around.
Should I measure the exact floor area or round up?
Measure the longest length and width and multiply, rather than trying to net off every alcove, then apply the wastage percentage on top. This naturally builds in a sensible buffer without needing complex geometry.
Why do tile boxes never match my calculated area exactly?
Tiles are boxed in fixed coverage amounts set by the manufacturer, so you will almost always round up to the next full box. Buying slightly over your calculated need, rather than trying to hit the figure exactly, avoids a costly and time-consuming reorder.
Does tile size affect how much wastage I need?
Yes. Larger-format tiles waste more material per miscut and are less forgiving of small room irregularities, so we generally recommend 12% to 15% wastage rather than the 8% to 10% that suits smaller tiles in a simple room.
Can you work out the tile quantity for me?
Yes, an accurate take-off is part of our free survey, along with recommended wastage for your specific room shape and chosen pattern, so you order the right amount first time.