Work out the slabs or pavers, sub-base, sand and cement needed to lay a patio of any size.
Enter the overall patio length and width, pick your slab (paver) size, set the sub-base depth (100 mm / 4 in is typical for a patio), and add a waste allowance for cuts and breakages. The tool returns the number of paving slabs, the crushed-stone sub-base in tons/tonnes and the bedding mortar or sand.
| Layer | Depth |
|---|---|
| Sub-base (MOT Type 1 / crusher run) | 100 mm / 4 in |
| Bedding mortar or sand | 30–50 mm / 1–2 in |
| Slab joint gap | 8–10 mm |
| Waste allowance | 5–10% |
A 4 m × 3 m patio = 12 m². With 600 × 600 mm slabs (0.36 m² each) you need 12 ÷ 0.36 ≈ 34 slabs, plus 10% ≈ 37. The 100 mm sub-base needs ≈ 2.4 tonnes of crushed stone.
Tip: lay slabs to a slight fall (about 1:80) away from the house so rainwater drains off rather than pooling.
For a domestic patio, 100 mm of compacted MOT Type 1 over firm ground is usually enough. For a patio that takes vehicle loads, increase it to 150 mm.
A full mortar bed is strongly recommended for patios — it supports the whole slab and prevents rocking and cracking. Spot or dab bedding is not suitable for areas that take foot traffic.
Allow about 10% for a rectangular patio, or up to 15% if there are curves, angles or lots of cuts around features.
Typically a compacted MOT Type 1 sub-base, a mortar or sand-and-cement bedding layer, then your slabs. The estimator lists quantities for each.
Aim for a slope of about 1:80 (roughly 12 mm per metre) away from the house so rainwater drains off rather than pooling.
