How this calc works

Grout coverage is a function of four things: tile length, tile width, tile thickness, and joint width. The thinner the joints and the bigger the tile, the less grout you use; the smaller the tile (think mosaic) and the wider the joints, the more. This calc takes all four and estimates the grout you need so you are not over- or under-buying.

That is why a mosaic sheet and a large-format floor of the same area need wildly different amounts of grout — far more joint length per square foot on the small tile. A flat per-square-foot rule of thumb will be wrong for one of them; the dimensions are what make the estimate honest.

Common mistakes

The mistake is buying grout off a flat per-square-foot guess. Mosaic and large tile differ by several times in grout demand for the same floor; the joint length, not the floor area, drives it.

The second is mixing sanded and unsanded for the wrong joint. Narrow joints want unsanded, wider joints want sanded — buy the type your joint width calls for, not just the right quantity.

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