Calculator
Example Data Table
| Scenario | Area | Tile Size | Joint | Waste | Factor | Estimated Output |
|---|---|---|---|---|---|---|
| Garden patio | 18 m2 | 300 x 300 mm | 4 mm wide, 8 mm deep | 10% | 1.05 | ~ 8.4 L, ~ 16.8 kg, 4 bags (5 kg) |
| Walkway strip | 9 m2 | 600 x 300 mm | 5 mm wide, 10 mm deep | 12% | 1.00 | ~ 6.0 L, ~ 12.0 kg, 3 bags (5 kg) |
| Raised bed edge | 6 m2 | 200 x 200 mm | 6 mm wide, 12 mm deep | 15% | 1.10 | ~ 13.7 L, ~ 27.4 kg, 6 bags (5 kg) |
Formula Used
The calculator estimates grout by modeling grout lines per square meter and multiplying by the joint cross-section. It then applies a layout factor and a waste allowance.
- L, W are tile length and width in meters (converted automatically).
- Joint width/depth are also converted to meters for consistent units.
- Pattern factor increases grout use for extra cuts and lines.
- Waste covers handling losses, cleanup, and small mistakes.
How to Use This Calculator
- Choose a unit system that matches your measurements.
- Enter garden area using length x width, or total area.
- Add tile length and width, then joint width.
- Enable auto depth, or type the joint depth.
- Select a pattern factor for your laying style.
- Set waste percent, density, and bag details.
- Press Calculate, then export the CSV or PDF.
Joint Width Planning for Outdoor Pavers
Joint width drives grout use because it defines the joint cross-section. For garden patios, 3–6 mm suits tight tile work, while wider gaps fit rustic pavers and uneven edges. Many ceramic patio tiles use 4 mm; concrete pavers often run 6–10 mm. Wider joints tolerate movement better, but consumption rises fast. Compare 4 mm versus 6 mm here to preview bag counts and costs.
Depth Control and Bedding Considerations
Depth should match the space you will fill, not the full tile thickness. Many installers fill about 60–75% of tile thickness to create a durable cap. Auto depth uses 70% of thickness as a practical default. Deeper joints increase volume linearly. Small depth changes matter on large areas. If joints are raked deeper for channels or borders, enter a manual depth for a closer estimate.
Pattern Complexity and Line Density Effects
Layouts change how much grout line exists per square meter. Straight patterns usually have fewer cuts, while diagonal and herringbone layouts add intersections, trims, and short segments. The pattern factor scales volume to reflect extra linework. 1.05 fits offsets, 1.10 fits diagonals, and higher values suit mixed layouts. For mixed-size garden mosaics, choose a higher factor to capture added perimeter length.
Waste Allowance for Edges, Drains, and Cuts
Waste includes leftover mix in buckets, losses during cleanup, and small batches mixed to finish edges. Outdoor projects often need extra allowance for curves, planter rings, drain channels, and steps. An 8–12% setting fits tidy work, while 15–20% is safer for irregular shapes, textured pavers, and frequent cutting. Reduce waste by mixing smaller batches and rinsing tools between passes.
Converting Volume to Bags and Cost
Grout is bought by weight, so liters are converted to kilograms using density. Many mixes fall near 1.8–2.2 kg/L, but product labels may differ. Bags are rounded up to prevent shortages mid-job, which helps keep color consistent. Enter bag size and price to build a plan, then export CSV or PDF.
FAQs
1) Is this estimate suitable for garden pavers set in sand?
Yes, for planning quantities. Measure the joint space you will actually fill, then use a higher waste percent because sand-set pavers can have uneven gaps and more cleanup losses.
2) What density value should I use if I do not know it?
Start with 2.0 kg/L for a typical mix. If your product label lists coverage or density, replace the default for closer results. Keep waste as a separate buffer.
3) Why does smaller tile size increase grout needed?
Smaller tiles create more grout lines per area. More line length multiplied by the same joint cross-section yields higher volume, so mosaics or small pavers can consume significantly more grout.
4) When should I raise the pattern factor?
Increase it for diagonal, herringbone, borders, and mixed sizes. These layouts add short segments and intersections that raise total joint length and increase handling time.
5) Should I use auto depth or enter depth manually?
Auto depth is a practical default based on tile thickness. Enter depth manually if you are raking joints deeper, using unusually thick pavers, or following a manufacturer-specified fill depth.
6) Why are bags rounded up instead of exact weight?
Running short can stop work and risk color mismatch if you buy later. Rounding up ensures enough material for finishing edges, touch-ups, and consistent mixing across the project.