How to Calculate Grout Quantity
The amount of grout you need depends on four factors: the tile size, the grout gap width, the tile thickness (depth of the gap), and the total area to grout. Smaller tiles with wider gaps need significantly more grout than large tiles with narrow gaps.
The formula used by our calculator is:
Grout (kg/m²) = [(Tile Width + Tile Height) / (Tile Width x Tile Height)] x Gap Width x Tile Thickness x Grout Density x 1000
The grout density is approximately 1.6 kg/litre for standard cementitious grout.
Grout Coverage Table
The table below shows approximate grout consumption for common UK tile sizes at standard gap widths:
| Tile Size | 2mm Gap | 3mm Gap | 5mm Gap |
|---|---|---|---|
| 100 x 100mm (mosaic) | 1.28 kg/m² | 1.92 kg/m² | 3.20 kg/m² |
| 200 x 100mm (metro) | 0.77 kg/m² | 1.15 kg/m² | 1.92 kg/m² |
| 300 x 300mm | 0.28 kg/m² | 0.43 kg/m² | 0.71 kg/m² |
| 450 x 450mm | 0.19 kg/m² | 0.28 kg/m² | 0.47 kg/m² |
| 600 x 300mm | 0.19 kg/m² | 0.29 kg/m² | 0.48 kg/m² |
| 600 x 600mm | 0.14 kg/m² | 0.21 kg/m² | 0.36 kg/m² |
Based on 8mm tile thickness and grout density of 1.6 kg/litre.
Types of Grout
Cementitious Grout (Standard)
The most common type in the UK. Available in sanded (for gaps 2mm+) and unsanded (for gaps under 2mm) versions. Brands include BAL Micromax, Mapei Keracolor, and Weber. Needs sealing for water resistance.
Epoxy Grout
Two-part grout that cures to a waterproof, stain-proof finish. Ideal for showers, wet rooms, and kitchen splashbacks. More expensive (£30-50 per 5kg) and harder to apply — work in small sections as it sets quickly. Brands include Mapei Kerapoxy and BAL Micromax Sealant Free.
Flexible Grout
Modified cementitious grout with added polymers for flexibility. Essential over underfloor heating, on plywood substrates, and for large-format tiles. Most modern grouts (BAL Micromax 2, Mapei Keracolor FF) are inherently flexible.
Grouting Tips
- Wait at least 24 hours after tiling before grouting (48 hours for large-format tiles)
- Mix grout to a smooth, lump-free paste. Let it slake (rest) for 5 minutes, then remix
- Work diagonally across the tiles with a rubber grout float
- Wipe excess with a damp (not wet) sponge before it hardens
- Do not walk on freshly grouted floors for 24 hours
- Seal cementitious grout after 7 days for stain protection (especially in kitchens and bathrooms)
Frequently Asked Questions
It depends on tile size and gap width. For 300x300mm tiles with a 3mm gap: approximately 0.43kg/m². For 600x600mm tiles: approximately 0.21kg/m². Mosaic tiles (100x100mm) need up to 1.92kg/m².
For 300x300mm tiles with a 3mm gap: approximately 11m². For 600x600mm tiles: approximately 24m². For mosaic tiles: approximately 2.5m².
Match grout to tile colour for a seamless look. Use contrasting grout for a grid effect. For floors, choose mid-tones (grey/beige) that hide dirt.
Sanded: for gaps over 2mm (most floor tiles). Unsanded: for gaps under 2mm (polished/glass tiles). Epoxy: waterproof, for wet areas.