Tile calculator
Give us the area and the tile size and we work out tiles and boxes.
Your inputs
Your inputs are processed on your device and are not sent to a server.
Example loaded. You can change any value.
There is no figure yet: nothing is calculated until you ask for it.
- Enter your measurements.
- Check the units and the assumptions.
- Press Calculate, or load the example.
Rather see a worked case? Press “Load example” and change any value afterwards.
Next step
Grout is worked out from the tile size and joint you have just entered.
Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates
How to use it
- Measure the area you are tiling.
- Enter the exact tile size in inches.
- Set the grout joint: it changes how many tiles fit per square metre.
- If you know how many tiles come in a box, we round up to whole boxes.
How it is calculated
The key to this calculation is that a tile does not take up its own size: it takes up its size plus a joint. Repeated hundreds of times, that gap changes the answer.
With a 24 x 12 in tile and a 2 mm joint, the module is 61.2 x 30.7 cm = 0.188 m², which is 5.3 tiles per square metre. Ignoring the joint would give 5.4: a small difference in a bathroom, three tiles across a whole house.
The result is always rounded up, because half a tile is not sold, and then grouped into boxes if you have entered how many pieces each box holds.
Worked example
A 13 x 10 ft floor with 24 x 12 in tiles, a 2 mm joint and 10 % waste:
- Area: 13 x 10 = 130 sq ft = 12.08 m²
- With waste: 12.08 x 1.10 = 13.29 m²
- Module with joint: 0.612 x 0.307 = 0.188 m²
- Tiles: 13.29 / 0.188 = 70.7 → 71 tiles
If a box holds 8, that is 9 boxes (72 tiles). The spare is not a rounding mistake: it is your replacement for the day one cracks and the range has been discontinued.
Good to know
- Waste follows the cuts. 10 % for a straight layout, 15 % for diagonal, up to 20 % for rooms with many corners or decorative borders.
- Large format, more breakage. A badly cut 48 x 24 in slab is wasted entirely. With large formats, raise the waste allowance.
- Keep the offcuts. Ranges are discontinued fast. A box in the garage is worth more than the money you saved by not buying it.
- Realistic minimum joint. Even with rectified tiles, leave 1.5-2 mm: the substrate does move.
Frequently asked questions
How many tiles do I need per square foot?
It depends on the tile size and the joint. A 24 x 12 in tile with a 2 mm joint gives about 0.5 tiles per square foot (5.3 per m²). A 12 x 12 in tile gives about 0.98 per square foot. The smaller the tile, the more the joint matters.
How much extra tile should I buy?
10 % for a straight layout in a regular room. 15 % for diagonal or herringbone patterns, or rooms with many alcoves. If this is your first tiling job, use 15 %.
Does the calculator account for grout lines?
Yes, which is why the answer differs slightly from dividing the area by the tile size. Each tile occupies its own size plus one joint on each shared edge.
How are boxes worked out?
If you enter the tiles per box, we divide the total by that number and round up. The leftover is shown so you know how many spares you end up with.
Does this work for walls as well as floors?
Yes. The maths is identical: area, tile size and joint. On walls, measure each section separately if the heights differ and add the areas together.
What about the grout itself?
That is a separate calculation because it depends on tile thickness. From the result you can jump straight to the grout calculator with your figures carried over.