®There’s no clever formula for ordering tiles. It’s the same sum the trade uses: area, plus wastage, divided by what one box covers, then round up. Where jobs go wrong is in the details around that sum: what you take off, what you leave on, and how much wastage you allow.
The sum
- Measure the area to be tiled, in square metres.
- Add a wastage allowance.
- Divide by the coverage printed on the box (for example, 1.44 m² per box).
- Round up. You can’t order 6.2 boxes.
If the box doesn’t state its coverage, work it out from the tile size and how many tiles are in the box.
What comes off the wall area
Doors and windows are holes, and you don’t tile holes, so their area comes off. Two things catch people out:
- A door with no height on the drawing. If it’s drawn floor to ceiling, you’ve just deducted a strip of wall you’re going to tile. Put the real door height in.
- Boxing in. Pipe boxes and bulkheads are surfaces, and they get tiled. Add boxing after the tiles were counted and the count has moved. Check it again.
What comes off the floor area, and what doesn’t
On the floor the rule isn’t about size. It’s about whether the floor underneath gets tiled.
| Item | Comes off the floor area? | Why |
|---|---|---|
| Shower tray or enclosure | Yes | It sits on the floor. Nothing is tiled under it. |
| Panelled bath | Yes | Boxed in to the floor. Nothing is tiled under it. |
| Freestanding bath | No | The floor runs under it, and you can see it. |
The freestanding bath is the one that bites. Treat it like a panelled bath and you under-order by its whole footprint: roughly 1.2 m² on a 1700 × 750 bath. You find out when the tiler runs out.
How much wastage?
Make it visible and make it a choice, not a number buried in a spreadsheet.
| Layout | Typical allowance |
|---|---|
| Straight lay, brick bond | 10–15% |
| Large-format tiles | More: one bad cut ruins a big tile |
| Herringbone or diagonal | 25–30% |
These are starting points. Confirm the final allowance against the actual tile, pattern and room before you order.
Gross area isn’t an ordering number
A rough “room coverage” figure, with nothing deducted, is handy for a first conversation. Don’t order from it. Order from the figure that has the openings, trays and panelled baths taken off and the wastage added back.
How KBB Go does it
In KBB Go each tile in the room gets its own card: the tile, the square metres it covers and the number of boxes. Openings, trays and panelled baths come off automatically, a freestanding bath doesn’t, and the wastage percentage is shown on the card so you can change it before quoting a herringbone floor. If a tile is missing its coverage or size, the card tells you which detail is missing instead of guessing. A guess reads as fact, and that’s how jobs run short.