How trowel notch size sets the mortar bed and the coverage per bag
A bigger notch lays a deeper bed for bigger tile — so it uses more mortar and covers fewer square feet per bag (¼″ square ≈ 80 sq ft/bag; ¾″ U-notch ≈ 30). Match the notch to the tile size.
What this diagram shows
Four tile-trowel notch sizes compared by the mortar ridges they leave and the coverage they give per bag. A ¼-inch by ¼-inch square notch suits tile up to about 8 inches and covers roughly 80 square feet per bag; a ¼-inch by ⅜-inch notch suits 8-to-12-inch tile at about 55 square feet; a ½-inch by ½-inch notch is for large tile (with an NTCA caution) at about 38 square feet; and a ¾-inch U-notch for large-format tile with back-buttering covers only about 30 square feet per bag. A bigger tile needs a bigger notch, which lays a deeper mortar bed, uses more mortar, and covers fewer square feet per bag.
Mortar / Thinset Calculator
Pick the right ANSI mortar (A118.1/.4/.11/.15/.3 or A136.1 mastic) for substrate and tile, then get bag count by trowel notch. NTCA, TCNA, ANSI A108.
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