How much extra tile should you buy?
Between 10 and 15 %, and there are concrete reasons for each.
10 % for a straight layout in a regular room and 15 % for diagonal, herringbone or awkward floor plans. With large-format tiles, use 15 % even laying straight.
Recommended waste table
Swipe to see the whole table
| Situation | Waste | Reason |
|---|---|---|
| Straight, rectangular room | 10 % | Cuts only at the edges |
| Straight, room with alcoves | 12-15 % | Every recess generates its own cuts |
| Diagonal | 15 % | Every row starts and ends on an angled cut |
| Herringbone or decorative mosaic | 15-20 % | Many cuts, few reusable offcuts |
| Large format (over 24 x 24 in) | 15 % | One bad cut wastes an expensive slab |
| First time tiling | +5 % | More tiles break than you expect |
Where the waste actually goes
It is not an arbitrary figure. Material is lost four different ways:
- Edge cuts. The last row is almost never whole, and the offcut only helps if the opposite wall needs a cut of the same size.
- Breakage when cutting. Large-format porcelain snaps badly if the cut is not clean.
- Defective tiles. Some arrive chipped from the factory or get damaged in transit.
- Mistakes. A mismeasured cut is one tile down, and it happens.
The waste is also your spare stock
There is an argument that rarely gets made: leftover tiles are the only realistic way to repair the floor a few years from now. Ranges are discontinued fast, and without spares a single cracked tile can force you to redo a whole area. Half a box in the garage is far cheaper than any alternative.
When it makes sense to reduce it
Going below 10 % only makes sense in one case: expensive tiles, a perfectly rectangular area, a straight layout and an experienced tiler who has already planned the cuts. Even then, below 7 % the risk stops being worth it.
Sources and methodology
These percentages reflect common site practice and are the editable defaults in the tile calculator. They do not come from a standard: they are widely shared trade judgement.
Frequently asked questions
How much extra tile should I order?
10 % for a straight layout in a regular room and 15 % for diagonal, herringbone or irregular plans. If this is your first tiling job, add another 5 %.
Why does diagonal laying waste so much?
Because every row begins and ends with an angled cut, and the leftover triangles rarely fit anywhere else. Laid straight, many offcuts start the next row.
Can I buy exactly the tiles I need?
It is risky and, more importantly, leaves you with no spares. One cracked tile three years from now, with the range discontinued, costs far more than the box you skipped.
Is waste applied to the area or to the tile count?
Mathematically it makes no difference: applying it to the area before dividing by the module gives the same answer as applying it to the tile count.