Tile Calculator
Enter area, tile format and waste allowance – get the exact quantity instantly
- Updated
Diagonal laying 15–20%, straight 10%, professional 5%.
Shopping list: packs, adhesive, groutgrout calculated · enter pack contents and adhesive
Printed on the pack – alternatively m² per pack
The joint is about as deep as the tile is thick
kg per m², depends on the notched trowel – printed on the bag
Tiles needed
245tiles
245For 20 m² you need 245 tiles of 30 × 30 cm: 223 for the area and 22 as waste allowance (10%).
- Area223 pcs91%
- Waste22 pcs9%
- Grout0.26 kg/m² from tile size, joint width and depth; density 1.6 kg/dm³ assumed – the manufacturer's figure takes precedence
- 5.1 kg · 2 bags of 5 kg
- Area per tile
- 0.09 m²
- Tile area to buy
- 22.05 m²
How this was calculated
Divide the area by the area of one tile, add the waste allowance and round up to whole tiles.
RZ-26 · headon.pro
Calculating tiles: formula, waste allowance and practical tips
Buying too few means a delivery delay, buying too many costs money – the formula explained
The tile formula is: quantity = ⌈area ÷ tile area × (1 + waste/100)⌉. For 20 m² and a tile of 30 × 30 cm (individual area 0.09 m²) with 10% waste, this gives: ⌈20 ÷ 0.09 × 1.10⌉ = ⌈244.4⌉ = 245 tiles. A 10% waste allowance is the recommended standard value for straight-laid tiles in a rectangular room.
Why waste is unavoidable: Cut-offs occur at every wall because room dimensions are rarely an exact multiple of the tile format. Corners, cutouts for sanitary fixtures, door frames and irregular room shapes further increase waste. Tiles laid diagonally (45°) produce noticeably more waste due to the angled cut lines at the edges – here 15–20% is realistic.
Grout pattern and tile adhesive: Besides the number of tiles, you need tile adhesive (also: thin-set mortar), grout and spacers. Tile adhesive is specified in kg/m² – typically 3–5 kg/m² with a 6–8 mm notch trowel. For floor tiles in wet areas, a deformable flexible adhesive is recommended (class C2 with S1/S2 per EN 12004; the "F" stands for fast-setting). Grout width affects the visual result: 2 mm for porcelain stoneware, 4–8 mm for handmade or rustic tiles.
Buy a reserve, same batch: Always buy 5–10 tiles more than calculated and keep them in reserve. Tiles are produced in batches – shade differences are possible when buying more from a different batch later. A reserve also protects against breakage during installation or later repairs. Broken or cracked tiles must be replaced before moisture gets under the floor.
Waste recommendations by installation method
Typical waste depending on installation and format
- Straight laying: 10%
- Standard for rectangular rooms; experienced DIYers may manage 8%
- Diagonal laying (45°): 15–20%
- More cutting waste along all four walls; more demanding for beginners
- Herringbone pattern: 15%
- Classic parquet-style pattern for elongated tiles (e.g. metro tiles)
- Large format ≥ 60×60 cm: 10%
- Fewer tiles, but heavier cuts; fewer grout lines
- Mosaic < 10×10 cm: 12–15%
- Many cuts, labor-intensive; often supplied on mesh sheets (calculate m²)
- Irregular rooms: +5%
- Niches, slopes and cutouts always increase waste
Calculation examples
- Area
- 20.00 m²
- Tile area (0.30 × 0.30)
- 0.09 m²
- ÷ 0.09 × 1.10
- 244.44
- Rounded up
- 245 tiles
- Area
- 12.00 m²
- Tile area (0.60 × 0.60)
- 0.36 m²
- ÷ 0.36 × 1.05
- 35.0
- Rounded up
- 35 tiles
Frequently asked questions about the tile calculator
Waste allowance, formats and costs for your tiling project
How much waste should I plan for when tiling?
The waste allowance depends on the installation method and format. For straight laying (parallel to the walls), a 10% surcharge is usually enough. For diagonal laying (45°), waste increases to 15–20%, since more material has to be cut off at the walls. For smaller formats under 15 × 15 cm, waste can also increase due to more cuts. For professionals and experienced DIYers working on simple areas, 5–8% is often enough.
What is the number of tiles without waste allowance?
The net tile count is the area in m² divided by the tile area in m². A 20 m² area with 30 × 30 cm tiles (0.09 m²) gives 222.2 → rounded up to 223 tiles without waste. With 10% waste, our calculator arrives at 245 tiles. The difference (22 tiles) corresponds to about 10% and covers typical cutting losses at walls, corners and cutouts.
Which tile formats are most common?
Classic formats are 20 × 20 cm, 25 × 25 cm and 30 × 30 cm. Modern bathrooms often use large-format tiles (60 × 60 cm, 60 × 120 cm or 80 × 80 cm). Large-format tiles have fewer grout lines and look more spacious, but are harder to install and require a perfectly level surface. Metro tiles (7.5 × 15 cm) are popular for kitchen splash-back areas.
Why are tiles always rounded up?
Tiles are indivisible units – you cannot buy 0.4 of a tile. That is why the calculated quantity is always rounded up to the next whole tile (ceiling function). It is also recommended to buy 2–5 extra tiles as a reserve. In case of damage or breakage, a reserve from the same batch (same pattern, same shade) is invaluable.
What does tile installation cost per m²?
In Germany, tradesperson costs for tile installation in 2025 range from €35–70 per m² depending on region (labor only, no material). Simple floor tiles in straight layout are cheaper than wall tiles or diagonal patterns. In addition, there are material costs for tile adhesive (€3–8/m²), grout (€2–5/m²) and cutting. As a DIYer, you save the labor share – but need a tile cutter, trowel and spacers.