How to Calculate Grout and Tile Adhesive Needed

Proper calculations for grout and thinset mortar ensure you buy enough material without excessive waste, and avoid the headache of a color mismatch from opening a second bag mid-project.

Grout Calculation Formula

Pounds of grout = (Tile length + Tile width) / (Tile length Γ— Tile width) Γ— Grout joint width Γ— Tile depth Γ— 0.1875

A simpler approach uses coverage tables from grout manufacturers (coverage in sq ft per pound varies by joint width and tile size).

Grout Coverage Reference

Tile Size1/8" Joint3/16" Joint1/4" Joint
4Γ—440–60 sq ft/lb25–35 sq ft/lb18–22 sq ft/lb
6Γ—660–80 sq ft/lb40–55 sq ft/lb25–35 sq ft/lb
12Γ—12115–130 sq ft/lb75–90 sq ft/lb50–65 sq ft/lb

Example: 150 sq ft bathroom floor, 12Γ—12 tiles, 3/16" joints At 80 sq ft/lb: 150 / 80 = 1.88 lbs β†’ buy 5-lb bag (always round up by bag size)

Thinset/Tile Adhesive

Coverage for thinset with standard ΒΌ Γ— ΒΌ inch notched trowel:

  • Small tiles (under 8"): 40–50 sq ft per 50-lb bag
  • Medium tiles (8–15"): 30–40 sq ft per 50-lb bag
  • Large tiles (16"+): 20–30 sq ft per 50-lb bag

For 150 sq ft with 12-inch tiles: 150 / 35 = 4.3 bags β†’ Buy 5 bags

Waste Factor

Add 10% for cuts and breakage; 15% for diagonal installation.

Use our tile calculator for any room size and tile format.