How much grout do I need per m²?

It varies hugely depending on tile size, joint width and tile thickness. Small metro tiles (100x200mm) with 2mm joints need roughly 0.5kg per m², while large 600x600mm floor tiles with 3mm joints need around 0.3kg per m². Our calculator gives you the precise amount based on your specific tile and joint dimensions.

What is the best grout joint width for wall tiles?

For most wall tiles in the UK, 2mm is standard. Metro tiles often suit 1.5mm for a sleeker look. Larger format tiles (300x600mm+) work well with 2-3mm joints. BS 5385-1 recommends a minimum of 2mm for wall tiles. Floor tiles typically need wider 3-5mm joints to allow for slight size variations.

Should I use sanded or unsanded grout?

For joints up to 3mm wide, use unsanded (fine) grout — this is standard for most UK wall tiling. For joints wider than 3mm (common on floor tiles and natural stone), use sanded grout which resists cracking in wider joints. Most UK grout brands like BAL, Weber and Mapei clearly state the recommended joint width range on the bag.

How long should I wait before grouting tiles?

Wait at least 24 hours after tiling with standard adhesive before grouting. With rapid-set adhesive, you can grout after 3-4 hours. The adhesive must be fully set before grouting — otherwise the pressure of grouting can shift tiles. In cold or damp conditions, allow extra drying time.

Do I need to seal grout in a bathroom?

Yes, it is recommended to seal grout in bathrooms and wet areas with a grout sealer after it has fully cured (usually 72 hours). Sealing prevents water absorption, staining and mould growth. Alternatively, use an epoxy grout which does not need sealing — though it is harder to apply and more expensive. Silicone sealant (not grout) should be used in all internal corners and where tiles meet sanitaryware. For wet room installations, see our wet room tanking calculator (/tiling/wet-room-tanking-calculator/) for waterproofing requirements.

Grout Calculator — How Much Grout Do I Need for Tiles UK

Grout Calculator — How Much Grout Do I Need?

Calculate exactly how much grout you need based on tile size, joint width and tile thickness. Uses accurate volume-based calculations for all standard UK tile sizes.

Total Tiled Area

Total area of tiling to grout

Tile Size

Joint Width

Standard wall tiles: 2mm, floor tiles: 3-5mm

Tile Thickness

Typical wall tile: 8mm, floor tile: 9-10mm

Bag Size

Include wastage allowance

Recommended for mixing and cleaning losses

Wastage Percentage

10% is standard for grout

Price Per Bag (optional)

Enter your supplier price for a cost estimate

How We Calculate This

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.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Grout Calculator — How Much Grout Do I Need?

How We Calculate This

The formula

Worked example

Grout density

Frequently Asked Questions

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