How Many Tiles to Buy: Cuts, Waste, Allowance and Boxes
Short answer: purchase quantity = net area + an allowance for cuts and breakage, converted to whole tiles and rounded up to whole boxes. Add the allowance only once. Illustrative example: for a 3.1 × 2.4 m floor (7.44 m²) with 60 × 60 cm tiles, the tile calculator with a 5% allowance gives 22 tiles, i.e. 6 boxes of 1.44 m² (24 tiles). For the same floor with the grout line in the centre, the 2D planner counts 24 pieces (8 full and 16 cut) and, with a 5% allowance, 26 pieces, i.e. 7 boxes.
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Net area and purchase quantity
The net area is what ends up covered: room length × width without the parts that are not tiled. The purchase quantity is larger because offcuts cannot always be reused, some tiles break when cut and a few should be kept for later repairs. The tile calculator does not subtract doors or windows, so enter net dimensions.
Full pieces, cut pieces and offcuts
Tiles are cut along the walls. An offcut can only be reused if it is large enough for another piece that is needed and the pattern direction allows it. In the grout-line-in-the-centre example the edge pieces at the shorter walls are 340 mm wide and the rest of the 600 mm tile is about 260 mm – too narrow for another such piece. So here every cut piece is in fact a new tile.
That is why the 2D planner calculates the purchase conservatively: it counts every cut piece as a new tile and does not include reuse of offcuts (except for planks where a row starts with the offcut). The cutting plan in the planner shows which offcuts can be reused, but it does not change the quantity to buy.
Tile calculator or 2D planner
The tile calculator works from the area with the selected allowance and assumes some offcuts are reused, so its result is closer to the net area. The 2D planner counts the actual full and cut pieces of the chosen layout and is more reliable when edge pieces are large and offcuts unusable. Use the calculator for a quick estimate and for adhesive and grout, and the planner for the number of tiles with large formats and visible edges. How allowance and packs are calculated step by step is described on the methodology page.
Example without adding the allowance twice
Illustrative calculation: floor 3.1 × 2.4 m, 60 × 60 cm tiles, 2 mm joint, box of 4 tiles (1.44 m²).
- Tile calculator: 7.44 m² × 1.05 = 7.81 m²; 7.81 ÷ 0.36 = 21.7, so 22 tiles; 7.81 ÷ 1.44 = 5.4, so 6 boxes (8.64 m², 24 tiles).
- 2D planner, Grout line in the centre, 0% allowance: 8 full + 16 cut = 24 pieces. This quantity already includes the cuts; waste relative to the purchased area is about 15%.
- 2D planner with a 5% allowance for breakage and repairs: 24 + 2 = 26 pieces, i.e. 7 boxes (28 tiles).
- Wrong: adding another 5% or 10% in the tile calculator on top of the 26 pieces from the planner – the allowance is then counted twice.
Transferring from the planner to the tile calculator
The “Transfer to the tile calculator” button passes the tiled area from the planner (7.39 m²) and suggests an allowance by pattern (5% for straight laying). The calculator then gives 22 tiles and 6 boxes; that is an area-based estimate, useful for adhesive and grout. When offcuts are unusable, as here, take the number of tiles to buy from the planner.
Rounding to packs
Enter the pack size from the label: m² per box or pieces per box; if both m² and pieces are given, enter m² per box. Boxes are always rounded up, and the planner shows the surplus from the last box as “Surplus pieces due to packs”. Without pack data the calculator shows only the number of pieces and does not assume a box size.
Buy all boxes at once, with the same batch and shade code on the box, because tiles bought later can differ in tone.
How to use the tile calculator – step by step
- 1. Add surfaces, choose Floor or Wall for each one and enter the dimensions in metres.
- 2. Choose the tile dimensions, from 20 × 20 to 120 × 120 cm (default 60 × 60 cm).
- 3. Choose the grout width: 1, 2, 3 or 5 mm (default 2 mm).
- 4. Choose the laying complexity: Simple (+ 5 %), Diagonal (+ 10 %) or Complex (+ 15 %).
- 5. Under Packaging enter m² per box or pieces per box. With Unknown you only get the number of pieces.
- 6. For floor surfaces you can turn on Self-leveling compound and choose a thickness from 1 to 30 mm.
- 7. Click Calculate, then save the calculation to a project or export a PDF.
Formula: how tiles, adhesive and grout are calculated
Required area = net area × (1 + allowance). Number of tiles = required area ÷ area of one tile, rounded up. Number of boxes = required area ÷ m² per box, or number of tiles ÷ pieces per box, rounded up to a whole box.
Adhesive: 5 kg/m², and for tiles with a side of 60 cm or more 6 kg/m² of required area. Grout in kg/m² = grout width (mm) × (a + b) ÷ (a × b) × 1.6, where a and b are the tile sides in cm. Adhesive is rounded up to 25 kg bags and grout to 5 kg bags. Self-leveling compound is calculated on the floor area without an allowance, at 1.7 kg/m² per mm, in 25 kg bags.
Calculation examples
Floor 4 × 5 m, 60 × 60 cm tiles, 3 mm joint, simple laying: 21 m², 21 ÷ 0.36 = 58.3, so 59 tiles. Adhesive 21 × 6 = 126 kg, 6 bags. Grout 0.16 × 21 = 3.36, so 4 kg, 1 bag.
Bathroom walls 2.0 × 1.6 m up to a height of 2.4 m, entered as four walls: 17.28 m², with a 5 % allowance 18.14 m². Tiles 60 × 30 cm (0.18 m²): 101 pieces. The format has a 60 cm side, so the adhesive comes to 109 kg, 5 bags. Grout with a 2 mm joint: 3 kg, 1 bag.
Hallway 3 × 4 m, 45 × 45 cm tiles laid diagonally, 3 mm joint, packaging 1.62 m² per box: 12 × 1.10 = 13.2 m², 66 tiles and 9 boxes, which is 14.58 m² or 72 pieces. Adhesive 66 kg, 3 bags. Grout 3 kg, 1 bag. Self-leveling compound 3 mm: 12 × 3 × 1.7 = 61.2, so 62 kg, 3 bags.
Adhesive and grout consumption by tile format
These are the values the calculator uses per m² of required area. Actual consumption depends on the substrate and the trowel, so the manufacturer's instructions apply.
| Tile format | Tiles per m² | Adhesive per m² | Grout 2 mm per m² | Grout 3 mm per m² | Grout 5 mm per m² |
|---|---|---|---|---|---|
| 20 × 20 cm | 25 | 5 kg | 0.32 kg | 0.48 kg | 0.80 kg |
| 30 × 30 cm | 11.1 | 5 kg | 0.21 kg | 0.32 kg | 0.53 kg |
| 45 × 45 cm | 4.9 | 5 kg | 0.14 kg | 0.21 kg | 0.36 kg |
| 60 × 30 cm | 5.6 | 6 kg | 0.16 kg | 0.24 kg | 0.40 kg |
| 60 × 60 cm | 2.8 | 6 kg | 0.11 kg | 0.16 kg | 0.27 kg |
| 120 × 60 cm | 1.4 | 6 kg | 0.08 kg | 0.12 kg | 0.20 kg |
| 120 × 120 cm | 0.7 | 6 kg | 0.05 kg | 0.08 kg | 0.13 kg |
60 × 60 cm tiles: how many per m²
One 60 × 60 cm tile is 0.36 m², so 1 m² takes 1 ÷ 0.36 = 2.78 tiles. With a 2 mm joint the centre-to-centre spacing is 60.2 cm and 2.76 tiles actually fit per m²; the calculator uses the nominal size, which gives a small extra margin. A box of 60 × 60 cm tiles usually holds 3 or 4 pieces (1.08 or 1.44 m²), depending on thickness and manufacturer – it is on the label.
- Illustrative example, tile calculator: 10 m² floor, simple laying (+ 5 %) = 10.5 m² → 30 tiles; adhesive 63 kg.
- Box of 4 pieces (1.44 m²): 8 boxes = 32 tiles (11.52 m²).
- Box of 3 pieces (1.08 m²): 10 boxes = 30 tiles (10.8 m²).
The most common mistakes when calculating tiles
- Buying without an allowance – the last row runs out of tiles and the new ones come from a different batch.
- Openings included in the area – the calculator does not subtract doors and windows, so enter net dimensions.
- The same adhesive consumption for every format – 60 cm formats need about 6 kg/m².
- Boxes guessed instead of taking the packaging from the label.
- A wider joint without adjusting the grout – a 5 mm joint uses two and a half times as much grout as a 2 mm joint.
- Self-leveling compound calculated for walls too – it is calculated for the floor only.
- Allowance added twice: once in the 2D planner and again in the tile calculator.
- Assuming every offcut can be reused even though it is narrower than the piece needed.
Sources and assumptions
The examples were calculated with the tile calculator and 2D planner functions of this app; they are illustrative calculations, not site data. Adhesive consumption (5 or 6 kg/m²) and the grout formula are calculator assumptions – real consumption depends on the notched trowel, the subfloor and the product data sheet.
Whole bathroom: floor, walls and levelling compound in one list
For a bathroom you do not need to calculate the floor, walls, levelling compound and levelling clips separately. The bathroom wizard takes the room, door, window and shower dimensions once, uses the same formulas as the tile calculator and merges identical items into one material list. Add waterproofing, silicone and skirting separately.
Frequently asked questions
Why does the 2D planner give more tiles than the tile calculator?
The planner counts every cut piece as a new tile, while the calculator works from the area plus a percentage allowance. When offcuts are unusable, the planner’s number is more realistic.
Should the allowance be added in both the planner and the tile calculator?
No. The planner’s piece count already includes the cuts; add only an allowance for breakage and repairs to it, and only once.
Can I calculate a floor and walls with different tiles together?
Not in one calculation: it uses a single tile format. For a 60 × 60 cm floor and 60 × 30 cm walls, do two calculations and save them to the same project.
How much grout do I need?
It depends on the format and the joint width: for 60 × 60 cm and a 2 mm joint about 0.11 kg/m², for 30 × 30 cm and a 3 mm joint about 0.32 kg/m². It is rounded up to 5 kg bags.
How do I calculate the number of tile boxes?
Under Packaging enter the m² or pieces per box from the label. The calculator rounds up to whole boxes and shows how many m² and pieces you are buying.
How many 60 × 60 tiles per m²?
2.78 tiles (1 ÷ 0.36 m²), about 2.76 with a 2 mm joint. Add a reserve for cuts and round up to whole boxes.