Tile Calculator

Tile quantity looks like simple division until you account for the grout joint. Each tile occupies its own footprint plus half a joint on every side, so the effective coverage of a twelve-inch tile with an eighth-inch joint is slightly larger than one square foot. Ignoring that overestimates the tile count marginally, but the effect grows quickly with small tiles and wide joints — with mosaic tile it becomes substantial.

The larger variable by far is layout. A straight, stacked layout only requires cuts at the perimeter, so waste stays around ten percent. Turning the grid forty-five degrees means every single edge tile becomes a diagonal cut with an unusable triangular offcut, which is why diagonal layouts need close to twenty percent. Herringbone is worse again, because the pattern itself generates cuts throughout, not just at the edges.

Large format tile — anything with a side over fifteen inches — changes the material requirements as well as the difficulty. It needs a bigger notched trowel to achieve adequate coverage behind the tile, which roughly halves how far a bag of thinset goes, and it typically needs a medium-bed mortar formulated not to slump under the weight. Large tiles are also far less forgiving of an uneven substrate, since they cannot flex to follow it and will either rock or crack.