Patio and Paving Calculator UK: Slabs, Blocks, Sub-Base and Mortar
Enter your patio or driveway size, then choose slabs, mixed-size packs or block paving. This paving calculator lists the slabs, MOT Type 1, bedding mortar, jointing and edging. It also gives the weight and dig depth, and the same patio calculator works for paths and driveways.
More free UK building calculators
A patio rarely stands alone. These calculators cover the sub-base, walls and driveways around it.
MOT Type 1, ballast, sand and gravel in tonnes and bulk bags.
Cubic metres, bags, cement and ballast for slabs and footings.
Sand, cement and hydrated lime quantities for brickwork, blockwork and repointing.
Bricks per m², mortar and cost for any wall.
Concrete, breeze and aircrete blocks, with mortar and cost.
Tiles per m², boxes and wastage for floors and walls.
Adhesive per m² and 20 kg bags by trowel notch.
Grout per m² from tile size, joint width and depth.
Litres and tins for rooms, walls, ceilings and exteriors.
Rise, going, pitch and stringer length, with Part K checks.
Tonnage, coverage and driveway cost per m².
Why patio estimates fall short
Picture this. The slabs arrive on a pallet, and the patio looks finished in your head. Then the mortar runs out with two rows still bare, and the sub-base looked thin from the start.
Paving is only the visible layer of a patio. Underneath sit the compacted sub-base, the bedding mortar and the jointing. Every layer needs ordering separately, and any one of them can interrupt the project halfway.
Plan it in layers: work out the paving, the MOT Type 1, the mortar bed and the jointing together. Then order everything for one delivery.
How many paving slabs per m²?
Each 600 × 600 mm slab covers 0.372 m² with its joint. That gives 2.69 slabs per m², so 10 m² requires 30 slabs including 10% for cutting.
How much sub-base and mortar per m²?
A 100 mm sub-base requires approximately 0.22 tonnes of MOT Type 1 per m². A 40 mm bed at 5:1 adds 71 kg of sharp sand and 13 kg of cement.
How to use the patio and paving calculator
Select the tab that matches your project, then complete the form from top to bottom. Most estimates take less than two minutes.
- Choose a calculation mode. Use Patio slabs, Patio packs, Block paving or Patio fall.
- Enter the area. Add rectangles for L-shapes, or use a circle or a known area in metres or feet.
- Specify the paving. Select the material, slab size and joint, or a block size and laying pattern.
- Configure the foundation. Enter the MOT Type 1 depth, then a mortar bed or a sand laying course.
- Add jointing and edging. Pick brush-in compound or 3:1 pointing, and add kerbs if needed.
- Add prices if available. Enter merchant prices and a labour rate to see the total and the cost per m².
The result displays a complete shopping list in bulk bags and 25 kg bags. It also provides the excavation depth and the weight of every material.
How many paving slabs do I need?
Every slab occupies its own footprint plus half a joint on each side. Therefore, divide the total area by the slab dimensions including one joint, then add wastage.
Paving slab calculator table: slabs per m²
| Slab size | Per m², 5 mm joints | Per m², 10 mm joints | For 10 m², with 10% |
|---|---|---|---|
| 600 × 600 mm | 2.73 | 2.69 | 30 |
| 900 × 600 mm | 1.83 | 1.80 | 20 |
| 600 × 300 mm | 5.42 | 5.29 | 59 |
| 450 × 450 mm | 4.83 | 4.73 | 53 |
| 600 × 450 mm | 3.63 | 3.56 | 40 |
| 300 × 300 mm | 10.75 | 10.41 | 115 |
| 750 × 600 mm | 2.19 | 2.16 | 24 |
| 800 × 800 mm | 1.54 | 1.52 | 17 |
| 1200 × 600 mm | 1.37 | 1.35 | 15 |
The last column uses 10 mm joints. Calculated with the tool on this page.
Patio calculator examples for real UK gardens
We ran each project through the paving calculator, including 10% paving wastage unless otherwise noted.
Case study 1: porcelain patio
A 5 × 3.6 m patio in 600 × 600 × 20 mm porcelain, with 5 mm joints
Porcelain has almost no suction, so prime the back of every slab with a slurry primer. At £60 a bulk bag and £8 a bag of cement, the base materials alone cost about £516.
Case study 2: Indian sandstone patio packs
The same 18 m² area in 22 mm calibrated sandstone, using four-size packs
Pack coverage already includes the joints. Choose the larger pack only if your patio requires few cuts.
Case study 3: block paving driveway
An 8 × 5 m driveway in 200 × 100 × 60 mm blocks, laid herringbone
Case study 4: patio fall
A patio 4 m deep, falling away from the house
Patio sub-base and mortar calculator: materials per m²
A durable patio requires a compacted MOT Type 1 sub-base and a continuous mortar bed. Dot-and-dab fixing leaves voids that crack slabs and trap frost.
| Layer | Per m² | Per 10 m² |
|---|---|---|
| MOT Type 1, 100 mm | 0.22 tonnes | 2.2 tonnes, about 3 bulk bags |
| MOT Type 1, 150 mm | 0.33 tonnes | 3.3 tonnes, about 4 bulk bags |
| Mortar bed 40 mm, 5:1 | 71 kg sand, 13 kg cement | 709 kg sand, 128 kg cement |
| Mortar bed 40 mm, 4:1 | 68 kg sand, 15 kg cement | 681 kg sand, 153 kg cement |
| Mortar bed 40 mm, 6:1 | 73 kg sand, 11 kg cement | 730 kg sand, 109 kg cement |
MOT Type 1 at 2.0 t/m³ plus 10% for compaction. Bed materials at 1.33 times the bed volume. Calculated with the tool on this page.
In our opinion, 5:1 suits most natural stone and concrete patios. Porcelain deserves the richer 4:1 mix and a slurry primer. Need a different sub-base depth or another aggregate? Our aggregate calculator handles every depth and alternative material.
Block paving calculator: blocks, sand and packs
Block paving quantities depend on the block size and pattern. The blocks rest on a compacted sharp sand laying course rather than mortar. Kiln-dried sand then interlocks the blocks through the narrow joints.
| Block size | Blocks per m² | Kiln-dried sand per m², 60 mm block |
|---|---|---|
| 200 × 100 mm | 50 | 4.4 kg |
| 160 × 120 mm | 52 | 4.3 kg |
| 160 × 160 mm | 39 | 3.7 kg |
| 240 × 160 mm | 26 | 3.1 kg |
| 200 × 200 mm | 25 | 2.9 kg |
Sizes include the spacer nibs. Jointing sand includes 10% for topping up after the first rain.
Current guidance puts the compacted laying course at 25–40 mm, as Paving Expert explains. The calculator orders 25% additional sand to allow for compaction. Herringbone creates the strongest driveway, but it requires about 10% wastage for edge cuts.
How many patio packs do I need?
Indian sandstone frequently arrives in four-size project packs. Mixing sizes creates a random pattern, but you purchase complete packs.
| Pack | 900 × 600 | 600 × 600 | 600 × 290 | 290 × 290 | Slabs |
|---|---|---|---|---|---|
| 15.25 m² | 13 | 13 | 13 | 9 | 48 |
| 18.95 m² | 16 | 16 | 16 | 12 | 60 |
Typical UK merchant packs. Coverage includes 5–10 mm joints, so check the label on yours.
Arrange the slabs dry before mixing any mortar. That way you can review the pattern and avoid continuous straight joints across the patio.
Patio fall calculator: how much slope?
Every patio needs a gentle fall, so rainwater drains away from the property. The usual minimum fall ratio is 1:80, which means 12.5 mm of drop per metre.
| Patio depth | Fall at 1:80 | Fall at 1:60 |
|---|---|---|
| 2 m | 25 mm | 33 mm |
| 3 m | 38 mm | 50 mm |
| 4 m | 50 mm | 67 mm |
| 5 m | 63 mm | 83 mm |
| 6 m | 75 mm | 100 mm |
Riven and textured stone drains more slowly, so 1:60 suits it better.
Keep the patio surface at least 150 mm below the damp-proof course. The Marshalls porcelain installation guide recommends this clearance. Limited height? Direct the fall towards a channel drain instead.
Paving slab weight calculator
Weight matters for van loads, deliveries and manual handling. Natural stone and concrete weigh considerably more than most homeowners expect.
| Material | Thickness | Weight per m² | Per 600 × 600 slab |
|---|---|---|---|
| Porcelain | 20 mm | 48 kg | 17.3 kg |
| Indian sandstone | 22 mm | 53 kg | 19.0 kg |
| Granite | 20 mm | 54 kg | 19.4 kg |
| Slate | 20 mm | 56 kg | 20.2 kg |
| Limestone | 25 mm | 65 kg | 23.4 kg |
| Concrete slabs | 35 mm | 81 kg | 29.0 kg |
Typical densities. Hand-pressed and riven slabs vary, so treat these as guides.
Patio cost calculator: what does paving cost in 2026?
We checked UK cost guides and merchant listings in October 2026. Laid prices vary widely with groundwork, access and region. Add your own prices to the patio calculator to see the total and the cost per m².
| Job or material | Typical price (2026) | Notes |
|---|---|---|
| Concrete slab patio, supplied and laid | about £35–£120 per m² | Lower figures exclude a full dig-out |
| Indian sandstone patio, supplied and laid | about £50–£160 per m² | Upper figures include excavation and sub-base |
| Porcelain patio, supplied and laid | about £65–£180 per m² | Large formats cost more |
| Block paving driveway, supplied and laid | about £70–£150 per m² | Most quotes £80–£120 per m² |
| MOT Type 1, bulk bag | about £44–£80 | Granite costs more than limestone |
| Sharp sand, bulk bag | about £42–£75 | Builders merchants vary widely |
| Cement, 25 kg | about £7.50–£8.50 | General purpose Portland cement |
Indicative ranges from UK cost guides and merchant listings. London and the South East often run 10–25% higher.
Paving a front garden in England? Hard surfacing over 5 m² needs planning permission unless it lets water drain through, according to GOV.UK guidance. Our patio permit guide covers back gardens too. Comparing a paved drive with tarmac? Try our tarmac calculator.
Patio and paving mistakes that cost money
Most patio failures originate underneath, not on the surface. These mistakes cause the cracked slabs and puddles we hear about most.
- Skimping on the sub-base. Soft clay needs 150 mm of MOT Type 1, compacted in layers.
- Dot-and-dab bedding. Individual mortar spots leave voids that crack slabs and trap frost.
- Insufficient fall. A level patio collects water and stains. Allow at least 1:80.
- Laying porcelain without primer. The mortar cannot bond, and slabs gradually loosen.
- Mixing batches. Natural stone varies between deliveries, so order everything together.
Setting kerbs or edging in concrete? Our concrete calculator works out the haunching. Building a garden wall around the patio? Our mortar calculator handles the brickwork mortar.
Paving calculator FAQs
How the paving calculator works out every layer
The patio calculator divides your area by each slab or block footprint, including the joint. It then adds your wastage and rounds up to whole slabs or packs.
MOT Type 1 uses 2.0 t/m³ plus 10% for compaction. Sharp sand uses 1.6 t/m³ and cement 1.44 t/m³. These densities match our aggregate and mortar calculators exactly.
Back to that pallet of slabs and the half-finished bed? Calculating every layer beforehand means one delivery and one finished patio. Prices checked in October 2026. Treat results as estimates, and follow your paving supplier’s instructions.
Are you laying a patio, a path or a driveway, and which paving have you chosen? Tell us through our contact page. Real projects help us improve the calculator.