Tile Grout Quantity Calculator
Grout fills the joints between tiles to the depth of the tile. The grout volume per square foot depends on the tile size, joint width, and tile thickness: smaller tiles and wider joints use far more grout. This calculator computes the joint volume from the tile dimensions, scales it by your floor area, and converts to weight and bags using the grout density from your product data. Density is product specific (sanded, unsanded, or epoxy differ), so it is a user input. The geometry is exact; add a bag for waste.
Grout quantity formula
Joint fraction = (tile L + tile W) / (tile L * tile W) ... per inch
Joint volume per sq in = joint fraction * joint width * tile thickness
Total volume (cu in) = joint volume per sq in * area * 144
Volume (cu ft) = total cu in / 1,728
Weight = volume (cu ft) * density; bags = ceil(weight / bag size)
The joint fraction captures how much joint length surrounds each tile. There are 144 square inches per square foot and 1,728 cubic inches per cubic foot. Density converts the grout volume to weight for bag counting.
Grout context
- Smaller tiles and mosaics have more joint per square foot and use much more grout.
- Grout volume scales directly with joint width: doubling the joint doubles the grout.
- Tile thickness sets the joint depth that grout must fill.
- Density differs for sanded, unsanded, and epoxy grout, so use your product value.
- Buy one extra bag for mixing loss, cleanup, and uneven joints.
Tile grout: frequently asked questions
How is grout quantity calculated?
Grout fills the joints around each tile to the tile's thickness. The joint volume per unit area equals (tile length plus tile width) divided by (tile length times tile width), times joint width, times tile thickness. Multiply by the floor area to get total grout volume, then by grout density to get weight, and divide by bag weight for bags.
Why do bigger tiles use less grout?
Larger tiles have less joint perimeter per square foot of floor, so they need less grout per square foot. Small mosaics have a lot of joint length packed into each square foot and use much more grout. That is why tile size is the dominant input in any grout estimate.
Does joint width matter a lot?
Yes. Grout volume scales directly with joint width, so a 1/4-inch joint uses roughly twice the grout of a 1/8-inch joint, all else equal. Wider joints are common with rustic or large-format tiles, so use the joint width your tile layout actually calls for.
What grout density should I use?
Density varies by grout type (sanded, unsanded, or epoxy) and brand, so it is a user input. Manufacturers publish coverage charts and the density needed to convert volume to weight. Enter the density or use the published coverage directly; this tool reports volume so you can match either method.
Should I add waste for grout?
A small waste allowance is wise, since some grout is lost in mixing, on the float, and in cleanup, and joints are rarely perfectly uniform. Buying one extra bag is cheaper than running out mid-job and risking a color mismatch between batches when you top up.
Official sources
- U.S. National Institute of Standards and Technology: NIST Unit Conversion (volume and density units).
- International Code Council: International Residential Code (ceramic tile).
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.