How to use the Patio Calculator
The patio calculator works out how many slabs and how much sub-base you need, with an allowance for cuts and breakages.
The formula
Slabs = patio area ÷ area of one slab, plus a waste allowance. Sub-base volume = area × depth.
Worked example
A 4 m × 5 m patio is 20 m². With 600 mm × 600 mm slabs (0.36 m² each) you need about 56 slabs, or 62 with 10% extra.
Tips for better results
- Add about 10% for cuts.
- Order everything from the same batch.
Common mistakes to avoid
- Forgetting the sub-base depth.
- Mixing millimetres and metres.
Please note: Results are estimates for general use. For safety-critical work such as electrical or building projects, check with a qualified professional and local codes. See our Disclaimer.