Paver Calculator
Works out pavers or slabs for a patio, path or drive, with the bedding sand. Enter the area and pick a size, or set your own.
Includes the waste allowance — this is the figure to order.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
units per m² = 1,000,000 ÷ ((face length + joint) × (face height + joint)) units = area × units per m² × (1 + waste)
Each unit effectively occupies its own face plus one joint along two edges, because the joint is shared with its neighbour. Working from the real face size and adding the joint is the only reliable way — nominal sizes already include the joint, so adding one again counts it twice.
What to watch out for
Paving is three layers and the pavers are the top one:
- Sub-base, 100–150 mm compacted. Crushed stone. This is what carries the load; skimping here is why patios sink.
- Bedding sand, 30–50 mm. Sharp sand, screeded, left uncompacted until the units are down.
- Pavers, with joints filled. Kiln-dried sand brushed in for block paving, mortar or jointing compound for slabs.
Lay a fall of about 1:80 away from any building — roughly 12 mm per metre. Flat paving against a wall puts water where you least want it.
Frequently Asked Questions
How many pavers do I need?
Divide the area by the size of one paver including its joint. A 20 m² patio in 600 × 600 mm slabs with 5 mm joints needs about 55 slabs, or 61 with 10% waste.
How much waste should I allow for paving?
10% for a plain rectangle, 15% for circles, diagonal laying or herringbone — patterns where nearly every edge piece has to be cut.
How deep should the sand be under pavers?
30–50 mm of sharp sand, screeded level and not compacted before the units go down. Deeper beds consolidate unevenly under load and the paving settles.