What size paving slabs are most common?

450x450mm and 600x600mm are most popular in the UK. 450mm slabs are easier to handle.

How much wastage for paving?

Allow 10% for cuts and breakages. More for diagonal patterns or complex shapes.

Do I need to account for joints?

For simplicity this calculator assumes tight-fit. With 10mm joints, you need slightly fewer slabs.

What is the best base for paving slabs?

A compacted sub-base of MOT Type 1 (75-100mm) topped with a 30-50mm layer of sharp sand or mortar. This provides a stable, well-drained foundation.

Should I lay slabs on sand or mortar?

Mortar gives a stronger, more permanent fix ideal for patios. Sand is easier for DIY and allows individual slabs to be lifted later. Use polymeric sand for joints.

GardenCalcs

Paving Slab Calculator — How Many Slabs

Calculate how many paving slabs you need for a patio or path.

Length

Width

Slab Size

Price per Slab (optional)

Include 10% wastage

How We Calculate This

Slabs = Area / Slab Area, rounded up. Wastage adds 10% for cuts and breakages.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.