What this calculator does
Paver count is the area divided by the area of one paver, plus waste. A 20 square metre patio in 400 by 400 mm pavers needs 138 units at 6.25 per square metre with a 10% allowance.
Paver size drives the count steeply. Dropping to 200 by 400 mm doubles the requirement to 275, because each unit covers half the area. Smaller units mean more laying time and more joints, though they also cut more efficiently around edges and curves.
The formula
The area with waste is divided by the area of a single paver. Bedding sand is the area multiplied by the bedding depth, and is calculated on the bare area rather than the area with waste, since sand is spread rather than cut. The figure excludes the compacted sub-base beneath, which is a separate and usually larger quantity.
| Term | Meaning |
|---|---|
| Bedding sand | The screeded layer pavers sit on, usually 25 to 30 mm. |
| Sub-base | Compacted crushed rock beneath the sand, typically 100 mm or more. Not included here. |
| Jointing sand | Swept into the gaps after laying, a small additional quantity. |
| Waste allowance | For cuts at edges and curves. 10% for a rectangle, more for a complex shape. |
The inputs explained
| Field | What to enter |
|---|---|
| Area to pave (m²) | Area to pave in square metres. |
| Paver length (cm) | Paver length in centimetres. |
| Paver width (cm) | Paver width in centimetres. |
| Bedding sand depth (mm) | Bedding sand depth. 25 to 30 mm is usual. |
| Waste allowance (%) | Waste allowance. Raise it for curves, diagonal laying or a herringbone pattern. |
When to use it
Ordering pavers for a patio
Pavers are sold by the unit or by the pallet, and the count decides the order.
Comparing paver sizes
Larger pavers lay faster but are heavier and cut less economically at edges.
Estimating the bedding sand
Sand is bought by the cubic metre and is easy to underestimate.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many pavers in each size?
The same area in a range of paver sizes.
| Paver length (400 mm wide) | Pavers needed | Pavers per m² | Bedding sand needed |
|---|---|---|---|
| 20 cm | 275 | 12.50 | 0.600 m³ |
| 30 cm | 184 | 8.33 | 0.600 m³ |
| 40 cm | 138 | 6.25 | 0.600 m³ |
| 60 cm | 92 | 4.17 | 0.600 m³ |
Questions
How deep should the bedding sand be?
Usually 25 to 30 mm of screeded sharp sand, laid over a compacted sub-base. Thicker bedding is not better: it allows pavers to settle unevenly under load. The load-carrying comes from the sub-base beneath, not from the sand.
Does this include the sub-base?
No, only the bedding sand. A patio typically needs 100 mm of compacted crushed rock beneath, and a driveway considerably more. That is usually the larger material quantity and needs calculating separately.
How much waste should I allow?
10% for a simple rectangle. Raise it to 15 or 20% for curved edges, diagonal laying or a herringbone pattern, all of which produce angled cuts whose offcuts cannot be reused.
What about jointing sand?
A separate and much smaller quantity swept into the gaps after laying. Kiln-dried or polymeric sand is used, and the amount depends on the joint width and paver depth. It is usually bought by the bag rather than calculated precisely.
For the bedding sand on its own, see the paver sand calculator. For a concrete alternative, see the concrete calculator.