Tile Calculator
Tile count for a floor or wall, waste included, plus boxes to buy.
Why the waste percentage is not optional
Every row that meets a wall gets cut, and the offcut is often unusable. Diagonal layouts, patterned tile and rooms with alcoves cut more. 10% covers a simple straight lay; go 15% for diagonals or small mosaic-heavy spaces. Also buy the waste NOW: dye lots vary, and matching a tile a year later is often impossible.
Grout lines
This estimate ignores grout gaps, which makes it slightly conservative (you'll need marginally fewer tiles than calculated). With standard 1/8 to 1/4 inch joints the difference is 2 to 4%, safely inside the waste allowance.