Block paving calculator

This calculator works from a rectangle. A real area rarely is one: a driveway often has a curve, there's a cut-out around a tree, one side runs along the house and the other along a fence that isn't parallel. A rectangle-based estimate is therefore always a starting point for ordering materials, not a basis for a binding quote.

The second difference is the laying pattern. The calculator applies a flat 8 % waste allowance, which works for a stretcher bond. With herringbone laid at 45 degrees and with three-size modular mixes, cutting happens all around the perimeter and actual consumption is higher. An exact figure only comes from tessellating the actual units across the actual shape.

The third thing is kerbs. Here they're calculated from the perimeter, rounded up. In practice, an off-cut from one corner gets used at the start of the next side, so real consumption tends to be lower. That's exactly where you can save — but only if someone keeps track of the off-cuts.

A quick check that catches most typos: multiply the area by the layer thickness in metres and by the density. For 50 m² and a 20 cm sub-base, that's 50 × 0.20 × 1.7, i.e. 17 tonnes of MOT Type 1. If your supplier quotes five tonnes, the thickness is wrong somewhere.

For pallets, remember they're sold whole. Seventeen square metres with waste rounds up to two pallets, even if a third of the second one is left over. That leftover is your reserve for repairs five years down the line, so don't throw it away.

Kerbs here are rounded up from the perimeter to whole metres, which is a safe estimate for ordering. In real installation, the off-cut from one corner gets used at the start of the next side, so actual consumption tends to be a bit lower. That's exactly where larger areas can save money — but only if someone keeps track of the off-cuts.