How Much Grout Do I Need?
Grout quantity depends on tiled area, tile dimensions, tile thickness and joint width. Smaller tiles and wider joints usually increase the amount required.
What affects grout use
More joint length, wider joints and deeper joints all increase grout volume. Manufacturer yield data should take priority when the product provides a specific coverage table.
Plan from the tile layout
Start with the net tiled area, then use the actual tile size and joint dimensions. Keep any extra allowance visible rather than hiding it in the estimate.