Tile size drives grout quantity — small tiles need far more grout than large ones

What this diagram shows

Three tiled fields of the same 2-foot-by-2-foot area compared at the same 1/8-inch joint width, with the grout joints shown in blue. A 2×2 mosaic packs 144 tiles and a dense web of joints and uses about 6.75 cubic inches of grout per square foot. A 12×12 tile has just four tiles and uses about 1.13. A 24×24 large-format tile is a single tile with almost no joints and uses about 0.56. At the same joint width the mosaic drinks roughly twelve times the grout of the large tile, because grout per square foot equals the perimeter-to-area ratio (L+W)/(L×W) times joint width times joint depth times 144 — joint length, not tile count, drives the total.