How to calculate how many tiles you need
- Measure the length and width of the floor or wall you are tiling. For L-shaped rooms, calculate each rectangle separately and add them up.
- Enter the tile size and the grout joint width.
- Pick an allowance for cuts: 10% is standard, 15% for diagonal or herringbone layouts.
- Enter the number of tiles per box to see how many boxes to buy.
How the tile count is worked out
Each tile covers its own area plus half of the grout joint around it, so the calculator divides the area by (tile width + grout) × (tile length + grout), then adds the waste allowance and rounds up. For example, a 3 × 2.5 m bathroom floor is 7.5 m². With 30 × 60 cm tiles and 3 mm joints, each tile covers about 0.183 m², so you need just over 41 tiles (42 rounded up) before extras, or 46 with 10%.
The extra covers tiles cut at the edges, around pipes and door frames, and the odd breakage. Large-format tiles, patterned layouts and rooms with many corners waste more. It is also wise to keep a few spare tiles from the same batch for future repairs, because colours vary between production runs. Imperial mode takes room sizes in feet, tiles in inches and grout in sixteenths of an inch. Everything is calculated in your browser.
How much extra tile should I buy?
10% for straight layouts, 15% for diagonal or herringbone, and up to 20% for small, complex rooms.
Does grout width change the number of tiles?
Slightly. Wider joints mean each tile covers a bit more area, especially with small tiles and mosaics.
How do I tile a wall with a window?
Calculate the full wall, then subtract the window area, but keep the waste allowance for the extra cuts.