How to Calculate the Correct Square Metres for Tiles (Without Mistakes)
Calculating the correct square metres of tiles is one of the most important steps in any renovation or new-build project. A small miscalculation can lead to material shortages, delays during installation, or difficulty matching the same tile batch later on.
In this guide, you’ll learn how to calculate tile quantities correctly, taking into account tile size, layout, waste allowance and real-life room conditions.
1. How to calculate the base square metres
The basic calculation is simple:
Length (m) × width (m) = square metres
Practical example
A room measures:
- 4.20 m × 3.60 m
👉 4.20 × 3.60 = 15.12 m²
This is the net surface area, but it is not the amount you should order.
2. Why the room size is not enough
When buying tiles, you must always account for:
- cuts along walls
- corners and recesses
- installation waste
- possible future replacements
For this reason, a waste allowance is always added to the net surface.
3. How much extra waste to add
The correct percentage depends on tile size and laying pattern.
Recommended guidelines
- Straight lay (standard formats) → +10%
- Large format tiles (80×80, 90×90, 120×120) → +10–12%
- Staggered or brick pattern → +12–15%
- Complex rooms (niches, corridors, many cuts) → +15%
Example
Room size: 15.12 m²
+ 10% waste = 16.6–17 m² to order
👉 Always round up, never down.
4. Calculating square metres for bathrooms and kitchens
Bathrooms and kitchens often require extra attention because:
- sanitary fixtures and furniture reduce usable space
- tiles may only be installed on selected walls
Practical tip
Calculate the entire surface area, even if part of it will later be covered by furniture. Ordering a few extra square metres costs far less than running short of tiles.
5. Special considerations for large format tiles
With large format porcelain tiles:
- cuts are more significant
- offcuts are harder to reuse
👉 Even in simple rooms, never go below a 10% waste allowance.
This is especially important for:
- 80×80
- 90×90
- 60×120
- 120×120
6. Why ordering everything at once matters
Ordering the full quantity in one single order is essential because:
- each production batch has its own shade and calibre
- future batches may not be identical
- some collections may become unavailable
👉 Ordering a small surplus upfront helps avoid serious issues later.
7. Quick summary
- ✔️ Calculate the real surface area
- ✔️ Always add a waste allowance
- ✔️ Increase waste for large formats or complex layouts
- ✔️ Round up, never down
- ✔️ Order everything in one single batch
Final thoughts
Correctly calculating tile quantities helps you save time, money and unnecessary stress. Adding the right waste percentage and ordering all tiles at once is the best way to ensure a smooth installation and a flawless final result.