Patio Paving Calculator
Instantly calculate how many paving slabs you need for your project. Accurate, free area estimator with built-in wastage calculations for DIY and professional landscaping.
Calculate Slab Quantity
Enter your patio dimensions and preferred slab size below to get an instant, precise estimate of the total number of paving slabs required, including a standard wastage allowance.
Patio Dimensions
Enter the measurements of your planned area
Material Estimate
Based on your input dimensions
Common Paving Slab Sizes
Standard slab dimensions and their approximate coverage per square metre to help you plan your purchase.
| Slab Size (mm) | Area per Slab (m²) | Slabs per 1 m² |
|---|---|---|
| 300 x 300 | 0.09 m² | ~11.1 slabs |
| 450 x 450 | 0.20 m² | ~4.9 slabs |
| 600 x 600 | 0.36 m² | ~2.8 slabs |
| 900 x 600 | 0.54 m² | ~1.85 slabs |
| 900 x 900 | 0.81 m² | ~1.23 slabs |
| 1200 x 900 | 1.08 m² | ~0.93 slabs |
Paving Calculation FAQ
Everything you need to know about estimating materials for your patio or driveway project.
To calculate the number of paving slabs needed, first find the total area of your patio by multiplying the length by the width (in metres). Then, divide this total area by the area of a single slab (in square metres). Finally, add 10% to the result to account for cutting wastage and breakages.
The industry standard wastage allowance for paving slabs is 10%. This accounts for slabs that may break during handling, cutting to fit edges or around obstacles, and natural variations in slab sizes. For complex patterns or irregular shapes, 15% is recommended.
This calculator uses the face-to-face dimensions of the slabs. While mortar joints (typically 10-15mm) do slightly reduce the effective coverage per slab, the recommended 10% wastage buffer comfortably absorbs this difference, ensuring you order enough materials.
For a standard domestic pedestrian patio, a compacted sub-base of 100mm to 150mm of MOT Type 1 aggregate is recommended, topped with a 30mm to 50mm layer of sharp sand or a full mortar bed, depending on your chosen laying method.