How the calculator works it out
Most online paver calculators divide the area by the size of one paver and stop there. That ignores the joint. With 3 mm joints, a 200 × 100 mm paver takes up 203 × 103 mm of ground, and the count drops by about 4 %. The calculator also works out the three layers underneath, which is where most first-time pavers under-order.
road base (t) = area × base depth × 2.2 · bedding sand (t) = area × bed depth × 1.5
jointing sand (kg/m²) = ( 1/L + 1/W ) × joint × thickness × 1,500
The jointing sand line assumes every joint is filled to the full depth of the paver. It lines up with the coverage one New Zealand jointing sand maker publishes: 3.3 kg/m² for 200 × 100 × 50 mm pavers and 1.1 kg/m² for 400 × 400 × 50 mm.
How many pavers per square metre?
Manufacturers' tables use the nominal count, with no joint. Real joints of 2–3 mm, or 4–6 mm for large formats, lower the count a little. The difference is small per square metre but adds up over a driveway.
| Paver (mm) | Typical thickness | Per m², no joint | Per m², 3 mm joint |
|---|---|---|---|
| 600 × 600 | 40–50 mm | 2.78 | 2.75 |
| 600 × 400 (bluestone) | 20–30 mm | 4.17 | 4.12 |
| 600 × 300 | 20–50 mm | 5.56 | 5.47 |
| 500 × 500 | 40–50 mm | 4.00 | 3.95 |
| 400 × 400 | 40 mm | 6.25 | 6.16 |
| 300 × 300 | – | 11.11 | 10.89 |
| 230 × 115 (clay brick paver) | 50 mm | 37.8 | 36.4 |
| 200 × 200 | 50 mm | 25.0 | 24.3 |
| 200 × 100 (Holland) | 50 or 80 mm | 50.0 | 47.8 |
Thickness depends on the traffic. Pavers up to 40 mm thick are for foot traffic only. The Concrete Masonry Association of Australia recommends 60 mm pavers for light vehicles and 80 mm laid in herringbone for heavier ones.
How deep should the base be?
Every Australian and New Zealand laying guide agrees on the order of the layers: compacted crushed rock, then a thin screeded bed of sand, then the pavers. They differ on the depth of the base, because it depends on the soil and the traffic.
| Source | Patio or path | Driveway | Bedding |
|---|---|---|---|
| Austral Masonry | 50 mm compacted road base | Concrete base recommended | 30 mm washed river sand |
| National Masonry | 100–150 mm road base, or 75 mm concrete | Engineer's advice; compact in 50 mm layers | About 30 mm coarse washed sand |
| Australian Paving Centre | 75 mm compacted | 150 mm compacted | 30 mm washed sand |
| Firth (NZ) | 50–75 mm GAP20/40 | 100–150 mm | About 20 mm |
| NZS 3116 (via Urban Paving, NZ) | 50 mm on average soil | 100 / 75 / 50 mm on weak / average / firm soil | 30 mm |
The calculator starts at 75 mm for foot traffic and 150 mm for a driveway, which sits in the middle of those ranges. On soft or reactive clay, or where water lies after rain, go deeper. The paver laying guide walks through each layer step by step.
Worked example: a 5 × 4 m patio in 400 × 400 pavers
- Area 20 m². Pavers per m² with 3 mm joints: 1 ÷ (0.403 × 0.403) = 6.16.
- Pavers: 20 × 6.16 × 1.05 for cuts = 129.3, so order 130.
- Road base: 20 × 0.075 m × 2.2 t/m³ = 3.3 t. At a 500 kg legal payload that is 7 loads in a 6×4 trailer, so pay for delivery (see the trailer load calculator).
- Bedding sand: 20 × 0.03 × 1.5 = 0.9 t.
- Jointing sand: (2.5 + 2.5) × 0.003 × 0.04 × 1,500 = 0.9 kg/m², so 18 kg.
- Dig depth: 40 + 30 + 75 = 145 mm below the finished paving level, plus the fall.
Fall and clearance from the house
Paving next to a house has to shed water away from it. In Australia the National Construction Code asks for the ground around a slab to fall at least 50 mm over the first metre. Paved surfaces in low-rainfall areas may fall 25 mm. The slab must sit at least 50 mm above paving that slopes away, and the brick damp-proof course usually 75 mm above it. In New Zealand, BRANZ recommends a 1:25 fall away from the building. E2/AS1 asks for the floor to be 100 mm above paving for brick veneer and 150 mm for other claddings. Never pave over weep holes or vents. Check these clearances before you dig, because they set your finished level.
Paver questions
How many 400 × 400 pavers do I need per square metre?
6.25 with no joint, or 6.16 with a 3 mm joint. Add about 5 % for cuts: a 10 m² area needs 65 pavers.
How much road base do I need under pavers?
Area × compacted depth × 2.2 t/m³. A 75 mm base under a patio is 0.165 t per m², so 1.65 t for 10 m². A 150 mm driveway base is 0.33 t per m².
Should I bed pavers on sand or crusher dust?
Most Australian paver makers specify washed river sand, and National Masonry says crusher dust is not recommended. Suppliers note it holds moisture and can cause white efflorescence staining. The industry association accepts crushed fines only when they are washed and meet its grading limits, so check with the paver maker before using crusher dust.
How deep do I dig for pavers?
Paver thickness plus bedding sand plus the compacted base. For 40 mm pavers on 30 mm of sand and 75 mm of road base, dig 145 mm below the finished level. A driveway with 60 mm pavers and a 150 mm base needs about 240 mm.
Sources and method
- Austral Masonry, Paver installation guide – base, bedding, joint widths.
- National Masonry, How to lay concrete pavers – road base depths, bedding sand, crusher dust.
- Adbri Masonry, Paver laying guide – pavers per m², 2 % allowance.
- Australian Paving Centre, DIY paving guide and paving area calculator – 75 / 150 mm bases, 5 % allowance.
- Firth, Paving installation guide (2026), and Dricon, PaveSand data sheet – NZ base depths and jointing sand coverage.
- Urban Paving, Installation guide for concrete pavers – base depths by soil strength from NZS 3116:2002.
- Concrete Masonry Association of Australia, PA02 Design of residential accessways and roads – paver thickness for vehicles, bedding thickness and grading.
- ABCB, NCC 2022 Housing Provisions Part 3.3 and Part 5.7 – surface fall, slab height and damp-proof course clearance; BRANZ, Build 570: Ground clearances – NZ.
- Densities: road base 2.2–2.4 t/m³ compacted and 1.9–2.1 t/m³ loose (Hunter Blue Metal, DGB20); washed river sand 1.5 t/m³. Example prices from ANL, September 2026.
Written by DueRiva · Last reviewed 23 September 2026 · Report an error