Block Paving Calculator — How Many Blocks Do I Need?

Our block paving calculator works out the number of blocks, sub-base materials, sand, and edging needed for your driveway or patio. It accounts for the extra wastage generated by different laying patterns. If the area is an L or T shape, add each rectangle as its own section: blocks are rounded up within each section (a cut cannot span the join), sub-base and sand use the combined area, and the edging figure adds the full perimeter of every section, an upper bound that over-orders at internal joins, so enter a measured edging run under Advanced options to trim it.

The formula

Blocks = Area × Blocks per m² × (1 + Pattern waste% + Extra waste%)
Sub-base = Area × Depth × 2,100 kg/m³ (2.1 t/m³ ordering density on the finished compacted depth, allowing ~20% compaction loss)
Sharp sand = Area × 0.035m × 1,600 kg/m³ (30-40mm laying course)
Kiln-dried sand = Area × 4 kg/m² (jointing — see range below)

Sub-base depth follows installation guidance in BS 7533-102:2025 (the current code of practice for modular paving, which superseded the withdrawn BS 7533-3 on 31 March 2025): 150mm compacted Type 1 MOT for domestic driveways, 100mm for patios. Kiln-dried jointing sand is typically 3.5 kg/m² for 50mm blocks rising to about 4.5 kg/m² for deeper 60mm joints; the 4 kg/m² default suits the standard 60mm driveway block and leaves a little for topping up after the joints settle. All material rates are adjustable under Advanced options.

Pattern wastage allowances

These are typical trade cut-waste allowances, not fixed standards — the exact figure depends on the shape of your area and the number of edge cuts. The relative ordering is what matters: a 45° herringbone needs the most cuts, stretcher bond the fewest.

• Herringbone 90°: ~5% (fewer edge cuts)
• Herringbone 45°: ~10% (most edge cuts)
• Stretcher bond: ~3% (minimal cuts)
• Basketweave: ~5%

Always confirm against your block manufacturer’s installation guide (e.g. Marshalls, Brett or Tobermore) and add extra for complex shapes, curves or radius cuts.