Tile Grout Quantity Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/8/2026
Grout quantity is calculated with (tile length+width)/(length×width) × grout line width × tile thickness × density, with an application margin. For 20 m² of 300×300 mm tiles, 4 mm grout line, you need about 8.9 kg of grout.
Explanation
Unlike tile adhesive (see the tile adhesive calculator), which fixes the tiles to the surface, grout fills the space between tiles once laid: these are two different materials, whose quantities are calculated separately. The amount of grout needed depends on the tile size (the smaller the tiles, the more grout lines per m², so more material), the chosen grout line width, and the tile thickness (the grout fills the gap over the full height of the tile). The formula used here is the one used by professional grout manufacturers, with a standard density of about 1.6 kg per liter for a classic cement grout — epoxy or resin-based grouts, denser and more expensive, follow a similar formula but with a different density, to check on the technical sheet of the chosen product. The margin factor included in the calculation already covers normal application losses (mixing, filling, cleaning): no additional margin needs to be added to the result obtained.
Example: 20 m² of 300×300 mm tiles, 4 mm grout line
Inputs
Surface: 20 m². Tiles: 300×300 mm, 8 mm thick. Grout line: 4 mm wide.
Calculation
Consumption per m² = (300+300)/(300×300) × 4 × 8 × 1.6 × 1.3 ≈ 0.444 kg/m². Total quantity = 0.444 × 20 ≈ 8.9 kg.
Result
You need about 8.9 kg of grout to tile this 20 m² surface.
Frequently asked questions
Why do smaller tiles consume more grout?
Because the number of tiles per m² increases when they are smaller, so the total length of grout lines between tiles also increases, for the same grout line width. A mosaic with small tiles thus consumes noticeably more grout than large-format tiling, for the same surface area.
Is the margin included in the calculation really enough?
This formula already includes a margin factor that covers normal application losses. For a first project or a complex installation (irregular shapes, many cuts), rounding the quantity up to the next bag when purchasing remains a reasonable precaution, the grout remaining usable for future maintenance.
Does the calculation change for epoxy grout instead of cement?
The calculation method (based on the volume to fill) stays the same, but the density used must be adjusted: epoxy grout generally has a different density from classic cement grout. Refer to the technical sheet of the chosen product for a more accurate result with this type of grout.