Start with net area
Measure each tiled surface and add the sections together before adding any waste. Applying a percentage to every small section and rounding each one separately inflates the order. Keep wall and floor tiles apart when their box coverage differs.
Apply one allowance to the total
Multiply the total area by one plus the waste percentage. For 12 m² with a 10% allowance that is 13.2 m². With 60 × 30 cm tiles sold in 1.44 m² boxes, the calculator gives 74 tiles and 10 boxes (14.4 m²). Raising the allowance to 15% gives 13.8 m² and 77 tiles, but still 10 boxes, because rounding up to whole boxes already covered the difference.
Choose the percentage for the layout
A straight layout in a plain rectangular room produces fewer offcuts than diagonal or herringbone patterns, rooms with many corners and pipes, or patterns that need matching. Large-format and fragile tiles also break more easily when cut. Where the tile maker or your fitter recommends a minimum allowance, use that figure.
Keep matching spares
Tile boxes usually carry shade and size codes. Buy every box with the same codes, and keep a few spare tiles from that batch for later repairs, because a later batch may not match exactly.
Practical checklist
- Round up to whole boxes only after adding the allowance.
- Check shade and size codes on every box before fixing any tiles.
- Confirm whether the supplier accepts unopened boxes back.
