Results update as you type. Round up when ordering.
Based on sanded cement grout (e.g. Polyblend, Mapei) at ~0.058 lb per cu in. Check the bag's coverage chart.
Formula checked against manufacturer specs
Rounded up to whole units
Runs in your browser
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.
It uses the standard formula shown on this page and rounds bags, boxes and pieces up to whole units. Product sizes vary by brand, so confirm with the label or your supplier before you buy.
Should I buy extra material?
Yes. A 5–10% allowance covers cuts, spills and uneven surfaces; running short mid-job usually costs more than a few leftovers.
Is this calculator free?
Yes. Every PorchMath calculator is free, needs no account and runs entirely in your browser.