How many 30 cm paving slabs for a 3 × 4 m patio?
A 3 × 4 m patio (12 square metres) in 30 × 30 cm pavers needs 147 pavers: 134 to cover it plus 10% for cuts. Underneath go about 3.14 tonnes of crushed sub-base (10 cm compacted, running 10 cm past the edges) and 0.33 cubic metres (330 litres) of bedding sand.
How to work it out
- 4 m × 3 m = 12 m²
- 12 m² ÷ (30 × 30 cm = 0.09 m²) + 10% (not sure yet) = 147 pavers
- To order by area: 12 m² + 10% = 13.2 m²
- Base area (base runs 10 cm past each edge): 4.2 × 3.2 m = 13.4 m²
- 13.4 m² × 10 cm = 1.34 m³ compacted
- 1.34 m³ compacted × 1.25 = 1.68 m³ loose × 1.78 t/m³ = 2.99 t
- + 5% waste = 3.14 t
- Effective rate: ≈ 2.34 t per m³ compacted
- Bedding sand: 12 m² × 2.5 cm + 10% for screeding = 0.33 m³, or 24 bags of about 25 kg
- Bulk sand: 0.33 m³ × 1.78 t/m³ (damp, typical) = 0.59 tonnes → order 1 tonne
- Joint sand: 14 L of joints 3 mm wide, filled to 3 mm below the top × 1,600 kg/m³ = 1 bag (22.7 kg) (about 12 m² per bag)
- Dig: 10 cm base + 2.5 cm sand + 6 cm paver = 18.5 cm → about 18.5 cm
- Soil out: 12 m² × 18.5 cm under the pavers + 1.44 m² × 10 cm base-only strip = 2.36 m³ in the ground × 1.25 = 2.96 m³ loose
- Edging: 14 m around; 1 spike per 30 cm = 46 spikes
Twelve square metres is a common small patio. This example assumes concrete block paving on a sand bed. UK-style natural stone slabs are often larger (60 × 60 cm or 60 × 90 cm) and are usually laid on a mortar bed instead, which changes both the dig and the materials.
Adjust for your project
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- Pavers to order by area (m², with extra)
- 13.2 m²
- Patio area
- 12 m²
- Base gravel (crusher run)
- 3.14 tonnes (3,140 kg)
- Bedding sand
- 0.33 m³ (330 L)
- Bedding sand in bags
- 24 bags (about 25 kg)
- Bedding sand, bulk weight (approx.)
- 0.59 tonnes (587 kg)
- Bedding sand, bulk order (rounded up to 0.5 t)
- 1 tonne
- Polymeric joint sand
- 1 bag (22.7 kg)
- Dig down about
- 18.5 cm
- Soil to remove (in the ground)
- 2.36 m³
- Soil to haul away (loose, about +25%)
- 2.96 m³
- Edge restraint
- 14 m
- Edging spikes
- 46 spikes
- Slope the patio about 2 cm per metre (2%) away from the house — never less than 1.5 cm per metre (1.5%, ICPI’s minimum) — and dig the excavation to the same slope.
- Bedding sand is screeded about 2.5 cm thick and never used to fill low spots; ICPI keeps it under about 4 cm.
- Dug soil fluffs up once it is out of the ground — typically 20–30%, more for clay — so the pile, trailer or dumpster needs room for the loose figure, not the in-ground one.
30 × 30 cm pavers for a 4 m long patio, by width
| Patio width | Pavers | Base gravel (crusher run) | Bedding sand |
|---|---|---|---|
| 2.5 m | 123 pavers | 2.65 tonnes | 0.28 m³ |
| 3 m | 147 pavers | 3.14 tonnes | 0.33 m³ |
| 3.5 m | 172 pavers | 3.63 tonnes | 0.39 m³ |
| 4 m | 196 pavers | 4.12 tonnes | 0.44 m³ |
What to know about a 3 × 4 m patio in 30 cm pavers
Each 30 × 30 cm paver covers 0.09 m², a little over 11 per square metre. The 3 m side divides into exactly 10 pavers, but the 4 m side is 13⅓: thirteen full rows and a strip only 10 cm wide. Thin strips crack and look fussy. Two better options: drop one full row and cut a 20 cm strip at each end (12 full rows plus 2 × 20 cm is 4 m), or stretch the patio to 4.2 m and lay 14 full rows with no cuts on that side.
- Sub-base. In the UK the usual sub-base is Type 1 (crushed stone graded down to dust, which compacts hard). The base runs 10 cm past each edge, so it covers 3.2 × 4.2 m, and it packs down by about a quarter: 3.14 tonnes is about four bulk bags if your merchant’s bags hold the common 850 kg or so — check what theirs hold.
- Sand. 0.33 m³ of sharp sand, including 10% for screeding, weighs roughly half a tonne; one bulk bag covers it with some left over.
- Dig. 10 cm of sub-base, 2.5 cm of sand and a 6 cm paver add up to an 18.5 cm dig. Under the pavers that takes out about 2.2 m³ of soil, plus a little more for the 10 cm strip of sub-base around them: about 2.4 m³ in the ground, and roughly 3 m³ once it is loose.
In imperial terms this is close to How many 16×16 pavers for a 12×12 patio; for a larger layout see How many pavers for a 12×16 patio.
Different size? Use the full Paver Calculator.
What you’ll need
- Hand tamper (8 × 8 in or 10 × 10 in)Budget price
Compacts gravel in small areas and along edges where a rented plate compactor won’t reach. For a whole patio base, rent the plate compactor.
See options on Amazon (opens in a new tab) - Paver screed rails / leveling kitBudget price
Rails and a straight board for screeding bedding sand to an even 1 in. Pipe and a 2×4 also work.
See options on Amazon (opens in a new tab) - Paver edge restraintBudget price
Holds the outside row of pavers so the patio doesn’t spread. Measure the perimeter — that is how much you need.
See options on Amazon (opens in a new tab)
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Frequently asked questions
How many 60 × 60 cm slabs for a 3 × 4 m patio?
37 pavers with 10% extra (12 m² ÷ 0.36 m² each). Large slabs are usually laid on mortar, so check the maker’s bedding instructions.
How many 20 × 10 cm block pavers for a 3 × 4 m patio?
660 pavers with 10% extra: 50 per square metre.
How much sub-base for a 3 × 4 m patio at 15 cm?
About 4.97 tonnes: the base runs 15 cm past each edge (3.3 × 4.3 m) and crushed sub-base packs down about a quarter. The dig goes to about 23.5 cm.
Other common sizes
- How many pavers for a 10×10 patio — 495 pavers
- How many 16×16 pavers for a 12×12 patio — 90 pavers
- How many pavers for a 12×16 patio — 564 pavers
Sources
- ICPI Tech Spec 2 — Construction of Interlocking Concrete Pavements (PDF, via ORCO) (opens in a new tab) — Base at least 4 in after compaction for patios on well-drained soil, 6 in for driveways, 2–4 in more on wet, weak or cold-climate soils; minimum slope 1.5%; bedding sand screeded to a nominal 1 in; 60 mm pavers for patios and driveways, 80 mm for streets; joints 1/16–3/16 in.
- ICPI / CMHA Guide Specification PAV-GSP-011-21 — Pavers on Aggregate Base (PDF) (opens in a new tab) — Base past the edge-restraint spikes at least the base thickness (up to 10 in); 80 mm pavers recommended for vehicular use, 60 mm allowed on residential driveways.
- ICPI Tech Spec 17 — Bedding Sand Selection (PDF, via ORCO) (opens in a new tab) — Bedding sand screeded loose 1–1½ in, compacting to about ¾–1¼ in.
- Oregon State University Extension — 10-Step Guide to Installing Pavers (PDF) (opens in a new tab) — 4–6 in base, 1 in bedding sand, 5–10% extra, slope 1 in per 4 ft, mark out about 8 in beyond the paved area, compact the base in layers.
- Belgard — Paver and Wall Installation Guidelines (opens in a new tab) — Compacted aggregate base 4–6 in deep; bedding sand at least 1 in.
- Techniseal — RG+ polymeric sand (opens in a new tab) — Narrow joints: about 60–120 sq ft per 50 lb bag, depending on paver size and joint width.
- Alliance Gator — Supersand G2 polymeric sand (opens in a new tab) — Fill joints to at least 1/8 in below the paver top; 65–85 sq ft per 50 lb bag on 2⅜ in pavers with narrow joints.
- Snap Edge — Engineering specifications for nail placement (PDF) (opens in a new tab) — 10 in spikes 12 in apart preferred; spacing 12–24 in depending on backfill.