Grout formula
Grout fills the joints around each tile. Volume per square foot = 144 × (L + W) ÷ (L × W) × joint width × joint depth, in inches. Multiply by area, then by grout density—cement grout is roughly 0.058 lb per cubic inch (about 1.6 g/cm³). Manufacturers publish their own coverage charts; use them when available.
Example: 100 sq ft of 12 × 12 in tile, 1/8 in joints, 3/8 in deep: 14,400 × 24/144 × 0.125 × 0.375 = 112.5 cu in ≈ 6.5 lb.
Sanded or unsanded?
- Unsanded: joints narrower than about 1/8 in, and easily scratched surfaces like polished marble
- Sanded: joints about 1/8 in and wider
- Epoxy: showers and kitchens where stain resistance matters
Small tiles have far more joint length—mosaics can need several times more grout than large-format tile.