Grout calculator
Grout fills the joints between tiles, so the amount depends on how many metres of joint there are in a square metre, how wide and how deep they are. Small tiles have many more joints than large ones — and therefore need several times more grout.
The calculator uses the formula published by grout manufacturers on their data sheets.
Your measurements
Result
- Estimated consumption
- 0.128 kg/m²
- Grout needed
- 1.3 kg
Add about 10% for mixing losses and cleaning; grout is sold in bags of 2–25 kg.
How the calculation works
- Consumption (kg/m²) = (A + B) ÷ (A × B) × C × D × 1.6, where A and B are the tile length and width in mm, C is the tile thickness in mm and D is the joint width in mm.
- 1.6 is the density of hardened grout in kg/dm³.
- Grout needed = consumption × tiled area.
Worked example
For 10 m² of 60 × 60 cm tiles, 8 mm thick, with 3 mm joints: (600 + 600) ÷ (600 × 600) × 8 × 3 × 1.6 = 0.128 kg/m², so about 1.3 kg for the whole floor.
What the calculator assumes
- The joints are filled to the full thickness of the tile.
- The density of 1.6 kg/dm³ is typical for cement-based grout; epoxy grouts can differ — check the data sheet.
When to adjust the result
- Add around 10% for mixing losses and cleaning off.
- With mosaic or small tiles (10 × 10 cm and below), consumption rises sharply — the formula already reflects this, so trust the result.
- Choose a flexible or epoxy grout for showers, floors with underfloor heating and outdoor areas, as recommended by the manufacturer.
Frequently asked questions
How much grout do I need per square metre?
For large 60 × 60 cm tiles with 3 mm joints, only around 0.1–0.15 kg/m². For 20 × 20 cm tiles with 3 mm joints and 8 mm thickness it's about 0.38 kg/m². The tile size matters more than anything else.
What joint width should I use?
Follow the tile manufacturer's recommendation. Rectified tiles can be laid with narrow joints of 2 mm; pressed tiles with small size variations need wider joints, around 3–5 mm.
Can I grout immediately after tiling?
No — wait until the adhesive has set, usually 24 hours for standard adhesive. Rapid-setting adhesives allow grouting sooner; the time is on the bag.