Grout calculator
Tile size, joint width, and area to pounds and bags — one neutral calculator, calibrated against the manufacturers' own coverage charts.
Calibrated to the manufacturer coverage charts below. Unsanded grout is for joints 1/8″ and under; sanded for wider joints. Bag counts include the 10% overage.
How the estimate works
Grout fills the joints, so the estimate is joint volume × grout density: (L + W) ÷ (L × W) × joint width × joint depth × density, per square foot of tiled surface. Joint depth is the tile’s thickness. We calibrated the density (110 lb/ft³ sanded, 105 unsanded) so the formula lands on Custom Building Products’ published coverage charts for standard tiles — the tables below are the manufacturer’s own numbers, reproduced as the authoritative reference.
Using Mapei? Keracolor S (sanded) is rated for 1/8–5/8″ joints and Keracolor U for narrow joints; Mapei publishes an interactive coverage tool rather than a chart and recommends 5–10% overage. This calculator’s estimate applies to any cement grout — joint volume doesn’t care about the label — with bag counts already including 10%.