Paving slab calculator
Work out how many paving slabs a patio takes, in 600 by 600, 450 by 450 and 600 by 300, plus the sub-base underneath.
Paving slab calculator
You need
- Area
- With cuts
| Format | Exact | Order |
|---|
UK suppliers publish two conventions that do not agree. The nominal figure ignores the joint: Tobermore prints 2.78 slabs per square metre for a 600 by 600. Allowing a 10mm joint gives fewer slabs per square metre, and which convention a merchant uses changes the order on a large patio.
Enter your measurements to see what to order.
One 600mm x 600mm slab covers 0.36 square metres, which is 2.78 per square metre.
How to work out how many slabs you need
- Measure the area in metres and multiply length by width.
- Add 10 percent for cuts. Covers cuts at edges and breakage in handling. Large flags break more than small ones.
- Divide by what one 600mm x 600mm slab covers, and round up. Suppliers do not sell part units.
How many many slabs for a given area
| Area | 600mm x 600mm slab | 450mm x 450mm slab | 600mm x 300mm slab |
|---|---|---|---|
| 10 m2 | 31 | 55 | 62 |
| 20 m2 | 62 | 109 | 123 |
| 40 m2 | 123 | 218 | 245 |
| 80 m2 | 245 | 435 | 489 |
| 120 m2 | 367 | 652 | 734 |
Every figure includes the 10 percent overage and is this page's own calculator, not a separate table that can drift from it.
What one 600mm x 600mm slab covers
| Format | Covers | Per m2 | Where |
|---|---|---|---|
| 600mm x 600mm slabNominal, no joint allowance | 0.36 m2 | 2.78 | UK |
| 450mm x 450mm slabNominal, no joint allowance | 0.203 m2 | 4.94 | UK |
| 600mm x 300mm slabNominal, no joint allowance | 0.18 m2 | 5.56 | UK |
Why the figures differ between suppliers
UK suppliers publish two conventions that do not agree. The nominal figure ignores the joint: Tobermore prints 2.78 slabs per square metre for a 600 by 600. Allowing a 10mm joint gives fewer slabs per square metre, and which convention a merchant uses changes the order on a large patio.
What goes underneath
Paving slab sits on layers that are ordered separately and by volume, not by the piece. Running short on the base is the failure that shows two winters later.
- MOT Type 1 at 150mm. Mainland Aggregates: 150mm depth when used as a driveway sub-base for car traffic.
- Sharp sand at 50mm. Mainland Aggregates: sharp sand should be laid at 50mm depth for block paving bedding.
How much extra to order
10 percent. Covers cuts at edges and breakage in handling. Large flags break more than small ones.