Paving is sold by the piece or by the pack, but a patio is measured in square metres. Turning one into the other is a division, followed by an allowance for the slabs you will cut and break.
Slabs per square metre
One slab covers its length times its width. A 600 × 600 mm slab covers 0.36 m², so a square metre takes 2.78 of them. A 450 × 450 mm slab covers 0.2025 m², which is 4.94 a square metre. A 200 × 100 mm block paver is 0.02 m², which is exactly 50 a square metre.
Wickes lists Marshalls slabs at 450 × 450 mm and 600 × 600 mm. Bunnings lists a 600 × 600 mm slab and a 200 × 100 mm paver. Other sizes work the same way; enter the size printed on the pack.
| Size | Area each | Per m² |
|---|---|---|
| 600 × 600 mm | 0.360 m² | 2.78 |
| 450 × 450 mm | 0.2025 m² | 4.94 |
| 200 × 100 mm | 0.020 m² | 50 |
A worked patio
A 12 m² patio in 600 × 600 mm slabs needs 12 ÷ 0.36 = 33.3 slabs before cuts. With 10% added, that is 13.2 m² of slabs: 36.7, rounded up to 37.
The same patio in 450 × 450 mm slabs is 66 slabs with 10%. In 200 × 100 mm blocks it is 660 blocks.
How much to add
Ten per cent suits a simple rectangle with a few cuts along one edge. Curves, a circle feature, or lots of cuts around drains and walls take more. A diagonal lay takes more again.
Buy from one batch if you can. Natural stone and some concrete slabs vary in colour between batches, and a spare slab kept back makes a future repair invisible.
What the count leaves out
The count is pieces only. It does not include joint gaps, edge restraints, the bedding layer or the sub-base. For the sub-base, the Gravel calculator gives bags and the Tonnes calculator gives bulk bags.
Joints make the real coverage a little larger than the slab face, so leaving them out errs on the side of slightly more slabs.
Figures are estimates for a shopping list. Check the pack or datasheet before you buy.