BuildCalcs Calculate the patio area
A rectangular 5 m × 4 m patio is 20 m². For an L-shape, split the plan into rectangles and add their areas. This is easier to verify than estimating the whole shape at once.
Theoretical slab counts
| Area | 600 × 600 mm | 600 × 450 mm | 450 × 450 mm |
|---|---|---|---|
| 5 m² | 14 | 19 | 25 |
| 10 m² | 28 | 38 | 50 |
| 15 m² | 42 | 56 | 75 |
| 20 m² | 56 | 75 | 99 |
| 25 m² | 70 | 93 | 124 |
| 30 m² | 84 | 112 | 149 |
Counts are rounded up to whole slabs and assume the entire slab face contributes to coverage. Joint widths, patterns and cuts are not modelled in this quick table.
Worked example
A 20 m² patio using nominal 600 × 600 mm slabs has a slab face area of 0.36 m². 20 ÷ 0.36 = 55.56, therefore the theoretical minimum is 56 whole slabs. A practical order may be higher once the layout is considered.
Why pattern changes the answer
A single-size grid can use material differently from a mixed-size pattern. Edge cuts may sometimes be reused elsewhere; sometimes they cannot. The calculator gives a transparent quantity, but the laying plan remains important.
Don't forget the layers beneath
Slab count is only one quantity. Sub-base and bedding materials are volume calculations based on area and depth. Keeping these calculations separate makes assumptions easier to check.
Measurement checklist
- Measure the actual paved footprint.
- Confirm slab dimensions, not just product name.
- Sketch the pattern and likely edge cuts.
- Round physical slab counts upward.
- Check pack quantities before buying.
Enter your actual measurements rather than relying on a generic example.
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