Patio slab calculator
Work out how many paving slabs you need for a patio from its area and your chosen slab size, with an allowance for edge cuts.
Result
Slabs required
How to use this tool
- Measure the patio area.
- Enter your paving slab's length and width in millimetres (600 × 600mm is a common size).
- Read the number of slabs to order.
Assumptions
- Assumes a simple rectangular patio; irregular shapes or curved edges need a higher waste allowance.
- Does not account for a mixed-size random-lay pattern — that needs per-size quantities from the supplier's pack ratio.
Technical details: what the fields mean
- Patio area
areaM2 - Total patio area, in square metres.
- Slab length
slabLengthMm - Slab length, in millimetres.
- Slab width
slabWidthMm - Slab width, in millimetres.
- Waste allowance
wastePercent - Extra slabs for edge cuts around the patio's perimeter.
Methodology
Slabs = (area × (1 + waste%)) ÷ slab area, where slab area = (length ÷ 1000) × (width ÷ 1000). Rounded up to a whole slab.
Worked example
15m² patio, 600 × 600mm slabs, 10% waste
Inputs: Patio area: 15 m², Slab length: 600 mm, Slab width: 600 mm, Waste allowance: 10%
Result: 46 slabs required
Practical guidance
- Order slabs from the same batch — colour can vary between production runs.
- For a random-lay multi-size pattern, buy pre-packaged project packs sized for your area rather than calculating a single slab size.
Common mistakes
- Entering slab dimensions in centimetres instead of millimetres.
- Underestimating waste on a patio with many curved or angled edges.
FAQs
How many 600x600mm slabs do I need for 15m²?
46 slabs, allowing the default 10% waste for edge cuts.
Last reviewed: 2026-09-24
Assumes a single slab size in a simple grid layout — random-lay patterns need supplier project-pack quantities instead.
This tool provides an indicative estimate, based on the assumptions stated above.
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