Grout Calculator — How Much Grout Do I Need?

Our grout calculator uses a volume-based formula to determine exactly how much grout you need. Rather than rough estimates, we calculate the actual volume of grout joints per square metre based on your tile dimensions, joint width and tile thickness.

The formula

Grout (kg) = Area × Joint length per m² × Joint width × Tile thickness × Grout density

Joint length per m² is calculated as: (1000 ÷ tile width) + (1000 ÷ tile height), giving the total linear metres of grout joint in every square metre of tiling.

Worked example

For 10 m² of 300×600mm tiles with 2mm joints and 8mm tile thickness:

• Joint length per m² = (1/0.3) + (1/0.6) = 3.33 + 1.67 = 5.0 m/m²
• Grout volume per m² = 5.0 × 0.002 × 0.008 = 0.00008 m³
• Grout weight per m² = 0.00008 × 1800 = 0.144 kg
• Total grout = 10 × 0.144 = 1.44 kg, so 1 × 2.5kg bag or 1 × 5kg bag

Grout density

We use a grout density of 1,800 kg/m³ which is the industry average for cementitious grout. Coverage rates align with manufacturer data from BAL, Weber, Mapei and Dunlop. We recommend adding 10% wastage for mixing losses and cleaning.