Grout Calculator
Grout lives in thin gaps, but the total length of those gaps grows inversely with tile size. The joint volume in one square metre is (2 ÷ tile side) × joint width × joint depth; multiply by density, typically 1,600 kg/m³, for the weight per square metre. A 30 cm tile with 3 mm joints 8 mm deep takes 0.26 kg/m²; 2.5 cm mosaic still needs 1.02 kg/m² even with thinner 2 mm joints only 4 mm deep — exactly four times as much. Joint width and tile size set the answer together.
Your numbers
Grout needed
2.82kg
Grout per m²
0.256kg
Litres
1.6L
Formula
Grout per m² = 2 ÷ (Tile side ÷ 100) × Joint width (mm) ÷ 1000 × Joint depth (mm) ÷ 1000 × Grout density, Grout needed = Area × Grout per m² × (1 + Waste allowance ÷ 100)
Joint depth is normally the tile thickness. Manufacturer coverage tables assume one tile format, so carrying them across to mosaic or large-format tile is badly wrong. Mixed grout stiffens, so gauge only what you can use.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Area (m²)The space a shape covers — length squared. | 10 | 0 and up |
| Tile side (cm)One edge of a single tile. | 30 | 0 and up |
| Joint width (mm)The gap between tiles — the size of the spacers you use. | 3 | 0 and up |
| Joint depth (mm)How deep the joint fills, normally the same as the tile thickness. | 8 | 0 and up |
| Grout density (kg/m³)The set density of the grout; cement-based runs 1,500–1,700 kg/m³ and is on the bag. | 1,600 | 0 and up |
| Waste allowance (%)The extra bought to cover breakage and offcuts. | 10 | 0 ~ 50 |
Step by step
Quick reference table
Results when only Area (m²) changes and everything else stays put.
| Area (m²) | Grout needed (kg) | Grout per m² (kg) | Litres (L) |
|---|---|---|---|
| 5 | 1.41 | 0.256 | 0.8 |
| 7.5 | 2.11 | 0.256 | 1.2 |
| 10 | 2.82 | 0.256 | 1.6 |
| 15 | 4.22 | 0.256 | 2.4 |
| 20 | 5.63 | 0.256 | 3.2 |
What each result means
| Result | At default values |
|---|---|
| Grout needed (kg)The weight of grout to buy, waste included. | 2.82 |
| Grout per m² (kg)Grout to fill one square metre; smaller tiles push it up. | 0.256 |
| Litres (L)Capacity in litres; one litre is 1,000 cm³. | 1.6 |
Common mistakes
Joint depth is normally the tile thickness. Manufacturer coverage tables assume one tile format, so carrying them across to mosaic or large-format tile is badly wrong. Mixed grout stiffens, so gauge only what you can use.
Glossary
- Area
- The space a shape covers — length squared.
- Tile side
- One edge of a single tile.
- Joint width (mm)
- The gap between tiles — the size of the spacers you use.
- Joint depth (mm)
- How deep the joint fills, normally the same as the tile thickness.
- Grout density
- The set density of the grout; cement-based runs 1,500–1,700 kg/m³ and is on the bag.
- Waste allowance
- The extra bought to cover breakage and offcuts.
- Grout needed
- The weight of grout to buy, waste included.
- Grout per m²
- Grout to fill one square metre; smaller tiles push it up.
- Litres
- Capacity in litres; one litre is 1,000 cm³.
Frequently asked questions
Q. How is Grout Calculator calculated?
Grout per m² = 2 ÷ (Tile side ÷ 100) × Joint width (mm) ÷ 1000 × Joint depth (mm) ÷ 1000 × Grout density, Grout needed = Area × Grout per m² × (1 + Waste allowance ÷ 100) — Grout lives in thin gaps, but the total length of those gaps grows inversely with tile size. The joint volume in one square metre is (2 ÷ tile side) × joint width × joint depth; multiply by density, typically 1,600 kg/m³, for the weight per square metre. A 30 cm tile with 3 mm joints 8 mm deep takes 0.26 kg/m²; 2.5 cm mosaic still needs 1.02 kg/m² even with thinner 2 mm joints only 4 mm deep — exactly four times as much. Joint width and tile size set the answer together.
Q. Can you walk through an example?
With Area 10m², Tile side 30cm, Joint width (mm) 3, Joint depth (mm) 8, Grout density 1,600kg/m³, Waste allowance 10%, the answer is Grout needed 2.82kg.
Q. What do I need to enter?
Enter Area, Tile side, Joint width (mm), Joint depth (mm), Grout density, Waste allowance. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Area (m²) moves the answer to Area (m²) 5 → Grout needed (kg) 1.41 and Area (m²) 20 → Grout needed (kg) 5.63. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Joint depth is normally the tile thickness. Manufacturer coverage tables assume one tile format, so carrying them across to mosaic or large-format tile is badly wrong. Mixed grout stiffens, so gauge only what you can use.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.