Tile calculator
Enter the room and the tile, and get the count including the tiles you will cut, crack, or ruin learning.
Why the waste allowance is not optional
Every tile that meets a wall gets cut, and the offcut is usually unusable. Ten percent is the standard allowance for a plain rectangular room laid straight. Push it to fifteen percent for a room with alcoves or angles, and to twenty for a diagonal or herringbone layout, where almost every perimeter tile becomes two triangles.
The other reason for extra is future repairs. Tile production runs vary in shade, and a batch bought two years later will rarely match. Keeping a handful of spares from the original run is the difference between replacing one cracked tile and re-doing a floor.
Box counts round up, because shops sell boxes rather than tiles. If you are close to a box boundary, buy the extra box rather than the exact count — the cost of a spare box is trivial against the cost of stopping work.
Questions
What waste percentage should I use?
Ten percent for a straight layout in a simple rectangular room, fifteen for irregular rooms, twenty for diagonal or herringbone patterns where perimeter cuts multiply.
Does grout width change the count?
Barely for normal joints, and the waste allowance absorbs it. Wide joints of half an inch or more on small tiles do add up — add the joint width to each tile dimension if that is your case.
Should I buy spares?
Yes, at least a few beyond the calculated total. Tile batches vary in shade, so a repair years later will not match unless the spares came from the same run.