Grout Calculator

Our Grout Calculator ensures you buy the right amount of material for your tiling project. Here's how to use it:

Step 1: Enter the tile length and width in millimeters (mm). For example, a standard subway tile is 75x150mm.

Step 2: Enter the tile thickness in millimeters (mm). Thicker tiles require more grout to fill the depth of the joint.

Step 3: Enter the desired grout joint width (mm). Floor tiles typically use 3–5mm; wall tiles use 1.5–3mm.

Step 4: Enter the total surface area to be tiled in square meters (m²). Subtract any areas where tiles won't be placed, such as fixtures or windows.

Step 5: Select your waste factor. A minimum of 10% is standard to account for spreading and cleaning waste.

Step 6: Click 'Calculate' to see the total grout needed in kilograms (kg) and pounds (lbs). Always round up to the nearest full bag available at your supplier.

The calculator estimates grout volume by treating the joints as a grid of rectangular channels:

Grout Required (kg/m²) = [(L + W) × J × T × D] / (L × W)

Where: - L = Tile Length (mm) - W = Tile Width (mm) - J = Joint Width (mm) - T = Tile Thickness (mm) - D = Grout Density (Standard is ~1.7 kg/L)

Example: For 300x300x10mm tiles with 3mm joints: [(300 + 300) × 3 × 10 × 1.7] / (300 × 300) = [600 × 30 × 1.7] / 90,000 = 30,600 / 90,000 ≈ 0.34 kg per square meter. Including a 10% waste factor for 20m²: 0.34 × 20 × 1.10 = 7.48 kg.

Grout is the cementitious or epoxy material used to fill the spaces between tiles, locking them in place and protecting the edges from chipping. Getting the quantity right is essential because running short mid-project is a major disruption — grout batches can vary slightly in color, so it's always best to mix everything from the same batch for a consistent finish.

Not all grout is the same. Sanded grout contains fine sand for added strength and is used for joints wider than 3mm (typical for floor tiles). Unsanded grout is smoother and used for narrow joints (under 3mm) and delicate tiles like marble or polished glass that might be scratched by sand particles. Epoxy grout is highly resistant to stains and water, making it ideal for kitchen backsplashes and showers, though it is more difficult to apply than standard cement-based grout.

Proper application is key to a lasting finish. Always follow the manufacturer's mixing instructions to achieve a peanut-butter consistency. Apply the grout at a 45-degree angle to the joints using a grout float, ensuring the channels are completely filled. Wait for the grout to firm up slightly (usually 15–30 minutes) before wiping away the excess with a damp, not dripping, sponge. Avoid using too much water during cleanup, as it can weaken the grout and cause the color to fade or appear blotchy.