Planning a tile order: waste, boxes and spares
How tile size sets the count, why a waste percent matters more for some patterns, and how to turn tiles into whole boxes without coming up short.
Tile size decides the count, not just the area
Two rooms of the same square footage can need very different tile counts. The tool converts each tile's inch dimensions into square feet by multiplying width times height and dividing by 144, then inverts that to get tiles per square foot. A large format 18 by 18 inch tile covers 2.25 square feet, so you need fewer than half a tile per square foot, while a mosaic sized 6 by 6 needs four. Always size from a single tile, then let the area scale it up.
Why waste is not optional
Perimeter tiles almost always need cutting, and a saw takes a kerf out of each one. Corners, doorways, drains and pipe penetrations create odd offcuts that rarely fit anywhere else. On top of that, a few tiles chip or crack during handling and setting. A waste percent bakes all of this into the order so you are not stopping a job to make a second trip to the store, where a matching lot may be sold out.
How pattern changes the number
A simple grid aligned to the walls wastes the least, which is why 10 percent is a common baseline. Turning the field 45 degrees for a diagonal look forces triangular cuts along every edge and pushes waste toward 15 percent. Interlocking patterns like herringbone and basketweave waste more still, because each cut piece is a specific shape. When in doubt on a busy layout, add a couple of extra points of waste rather than gambling on exact cuts.
From tiles to boxes and spares
Tile is sold by the box, and the box count here rounds the total tiles up to the next full box. That rounding naturally leaves you a handful of spare tiles, which is exactly what you want. Keep at least a few sealed tiles from the same dye lot after the job, since color and shade can drift between production batches. Storing spares means a cracked tile years later can be swapped without a visible mismatch.