Paving Calculator

How Many Paving Slabs Do I Need?

This free paving calculator works out exactly how many slabs you need for your patio, garden path or driveway. Enter your area dimensions in metres or feet, choose a standard UK slab size (or enter a custom size), set your joint gap width, and get an instant answer showing the exact slab count, layout dimensions and wastage allowance.

The calculator accounts for the gap between each slab — something many people forget when estimating by hand. A 10mm joint gap across a 4-metre patio adds up quickly, and getting this wrong means ordering too many or too few slabs. Enter your measurements above and get the right number first time.

If you're laying paving on a new sub-base, you'll need aggregate underneath. Use our gravel calculator to work out how much MOT Type 1 or gravel you need for the foundation. Planning to fill raised beds next to your new patio? Our soil calculator works out the exact amount of topsoil or compost.

Types of Paving for UK Gardens

Choosing the right type of paving affects the look, durability and cost of your project. I have laid three different types over the years and each has distinct advantages. Here is what you need to know about the main options available in the UK.

Concrete Paving Slabs

Concrete slabs are the most affordable and widely available option in the UK. A standard 600 x 600mm concrete slab from B&Q or Wickes costs around £3–£6 each, making a 12 square metre patio achievable for under £200 in materials. They come in smooth, textured and riven (natural stone effect) finishes. The textured Bradstone slab is the best-selling patio slab in the UK for good reason — it is affordable, hard-wearing and looks decent from a distance. The downside is that concrete slabs can look uniform and slightly artificial compared to natural stone, and they are prone to algae growth in damp, shaded areas unless treated with a sealer.

Natural Stone Paving

Indian sandstone is the most popular natural stone paving in the UK, available in shades of buff, grey, brown and multi-coloured blends. Each slab has unique colour variation and texture, which gives patios a premium, character-filled appearance that concrete cannot replicate. Prices range from £20–£40 per square metre for budget Indian sandstone up to £60–£100 per square metre for premium Yorkstone or limestone. Natural stone is heavier than concrete — a 600 x 600mm Indian sandstone slab weighs around 30–35 kg compared to 22–25 kg for concrete. This matters when you are handling hundreds of slabs. Natural stone typically comes in patio packs with mixed slab sizes designed to be laid in a random pattern, so the calculator is most useful when used with the individual slab sizes within the pack.

Porcelain Paving

Porcelain paving has grown enormously in popularity in UK gardens over the past five years. It is made from kiln-fired ceramic and is extremely hard, non-porous and frost-resistant. Because it does not absorb water, porcelain paving stays cleaner than concrete or stone — moss and algae struggle to take hold on the smooth surface. It comes in finishes that convincingly mimic wood, stone or concrete at a fraction of the weight. Prices range from £30–£60 per square metre. The main downside is that porcelain requires a full mortar bed for installation (not just sand and cement like concrete slabs) and it needs special diamond-tipped blades to cut. If you are doing a DIY installation, factor in the cost of blade hire or replacement.

Block Paving

Block paving uses small bricks or blocks (typically 200 x 100mm) laid in interlocking patterns. It is the standard choice for driveways because it can flex with ground movement without cracking, and individual blocks can be lifted and replaced if they settle or stain. For patios, block paving gives a more traditional, cottage-garden feel. Blocks cost £15–£35 per square metre and are laid on a compacted sand bed over a MOT Type 1 sub-base. The main disadvantage is that block paving needs more preparation — proper edge restraints, a perfectly level sub-base, and kiln-dried sand brushed into the joints. Without these, blocks shift and weeds colonise the joints within months.

How to Lay Paving Slabs — Step by Step

Laying paving is one of the most satisfying garden projects, but the preparation underneath is what determines whether your patio lasts 20 years or starts sinking after the first winter. I learned this the hard way on my first patio — I skimped on the sub-base and had to relay half of it 18 months later. Here is the method that works properly.

Step 1: Plan Your Layout

Before digging, lay your slabs dry on the grass to check the layout and see how the pattern works. This is especially important with patio packs that have mixed sizes. Mark the finished patio outline with string lines and pegs. Allow a slight fall away from the house — a gradient of 1 in 60 is standard (roughly 17mm per metre). This ensures rainwater drains away from the building rather than pooling against the wall.

Step 2: Excavate

Dig out the area to a depth of approximately 150–200mm below your finished paving level. This allows for 100mm of sub-base, 30–40mm of mortar bed, and the slab thickness (typically 35–50mm). Use a spirit level on a straight edge to check that the base of the excavation follows your planned fall. Remove all turf, roots and organic material — anything left underneath will decompose and cause the paving to settle unevenly.

Step 3: Lay and Compact the Sub-Base

Spread 100mm of MOT Type 1 crushed stone across the entire area. Compact it with a vibrating plate compactor (hire for around £30–£40 per day) in two passes — once along the length and once across the width. The sub-base should be firm enough that you can walk across it without leaving footprints. Check the fall gradient is maintained across the compacted surface. Use our sub-base calculator to work out how much MOT Type 1 you need.

Step 4: Mix the Mortar Bed

For concrete and natural stone slabs, use a semi-dry mortar mix of 4 parts sharp sand to 1 part cement. Mix it until it holds together when squeezed but does not drip water — too wet and the slabs will slide, too dry and they will not bond. For porcelain paving, use a specialist primer and flexible adhesive mortar rather than a standard sand-cement mix, as porcelain does not bond well to ordinary mortar.

Step 5: Lay the Slabs

Start from a corner nearest the house and work outwards. Spread a 30–40mm bed of mortar slightly larger than each slab. Lower the slab onto the mortar and tap it level with a rubber mallet, checking with a spirit level as you go. Maintain consistent joint gaps using 10mm spacers (offcuts of tile spacers or plywood work well). Work across the patio one row at a time, checking the alignment with string lines after every 3–4 slabs.

Step 6: Point the Joints

Wait at least 24 hours for the mortar bed to set before pointing the joints. For a budget finish, use a 3:1 sand-cement mix pressed firmly into the gaps with a pointing trowel. For a professional, long-lasting finish, use a brush-in jointing compound — these are polymer-modified and resist weeds, ants and washing out in heavy rain. A 15 kg tub covers approximately 10–15 square metres of 600 x 600mm slabs and costs around £20–£35.

Step 7: Seal (Optional)

Applying a paving sealer within the first few weeks protects against oil stains, algae and frost damage. This is particularly worthwhile for natural stone, which is porous and stains easily. A 5-litre tin of sealer covers approximately 20–25 square metres and costs £25–£40. Porcelain paving does not need sealing.

How Much Does a Patio Cost in the UK?

The total cost of a patio depends on the size, paving type, and whether you do the work yourself or hire a professional. Here are realistic 2026 costs for the most common scenarios.

DIY material costs include slabs, sub-base, sand, cement and jointing compound. Professional installation costs include labour, skip hire and all materials. Prices vary by region — the South East is typically 20–30% more expensive than the Midlands or North for labour. Always get at least three quotes and ask to see recent examples of the contractor's work.

Common Paving Mistakes to Avoid

I have made some of these mistakes myself, and I have seen even more of them on gardening forums. Every one of these costs time and money to fix — some require ripping up and starting again.

Insufficient Sub-Base

The single most common paving failure in UK gardens is an inadequate sub-base. Without 100mm of properly compacted MOT Type 1 underneath, slabs settle unevenly over the first winter as water softens the soil below. I have seen patios that looked perfect in August develop 20mm dips and rock-able slabs by the following March. Skipping the sub-base saves maybe £100 on materials but costs ten times that to fix.

No Fall Away from the House

A level patio looks great in theory, but without a gentle slope away from the house, rainwater pools against the wall and can cause damp problems. The standard fall is 1 in 60 — that is 17mm per metre. On a 4-metre deep patio, the far edge should be about 67mm lower than the edge against the house. Check this with a spirit level and straight edge during construction, not after.

Weak Mortar Mix

Too much sand in the mortar mix means slabs loosen and rock within a year. The correct ratio is 4:1 (four parts sharp sand to one part cement) for concrete and stone slabs. Do not use soft building sand — it does not have enough grit to create a strong bond. And never use mortar that has started to set — once cement begins to hydrate, re-mixing it weakens the final strength significantly.

Forgetting Edge Restraints

Slabs at the edge of a patio need something to butt against, otherwise they gradually shift outward under foot traffic. Use concrete haunching (a wedge of mortar) along all exposed edges, or install a purpose-made edge kerb. This is particularly important for block paving, where the entire surface can spread outward without proper edge restraints.

Cutting Corners on Jointing

Ordinary sand-cement pointing washes out in heavy rain and provides a perfect environment for weeds and ants. Within two years, you end up with grass growing through every joint. Spending £25–£35 on a proper brush-in jointing compound saves you from re-pointing the entire patio every spring. It is one of the most worthwhile upgrades for any paving project.

Patio Maintenance — Keeping Your Paving Clean

A well-laid patio needs very little maintenance, but a yearly clean makes a dramatic difference to its appearance. Here is what I do each spring to keep my paving looking fresh.

Pressure Washing

An annual pressure wash removes the build-up of dirt, algae and moss that accumulates over winter. Use a fan nozzle rather than a pinpoint jet — the concentrated jet can damage jointing compound and erode the surface of softer stone. Keep the nozzle at least 300mm from the surface and work in overlapping passes. A domestic pressure washer (100–150 bar) is sufficient for most patios. Hire one for around £30–£40 per day if you do not own one.

Algae and Moss Treatment

In shaded areas, algae can return within weeks of pressure washing. Apply an algae treatment solution after washing — these typically contain benzalkonium chloride and keep surfaces clear for 6–12 months. Spray it on, leave it to work (do not rinse), and the algae dies back over a few days. Avoid bleach-based cleaners on natural stone as they can cause discolouration.

Re-Pointing Joints

Check your paving joints each spring. If sand-cement pointing has washed out or cracked, clear out the loose material and re-point with fresh mortar or a brush-in compound. Catching deteriorated joints early prevents weeds establishing deep roots and stops water getting under the slabs, which accelerates frost damage in winter.

Stain Removal

Oil stains from barbecues are the most common patio stain. Treat fresh oil spills immediately with cat litter — pour it over the stain, leave it for 24 hours, then sweep it up. For older stains, proprietary paving oil removers work well on concrete slabs but may need multiple applications on porous natural stone. Rust stains from metal furniture can be removed with a specialist rust remover — do not use vinegar on limestone as it reacts with the stone.

Standard UK Paving Slab Sizes

Not sure which slab size to use? Here are the most common sizes available from UK suppliers, how many you need per square metre, and the approximate weight per slab for planning deliveries and handling.

Frequently Asked Questions

Best Paving Products UK 2026 — Our Top Picks

Whether you're laying a patio or a garden path, these are the most popular paving products and accessories available in the UK right now.

Links above are affiliate links — we may earn a small commission at no extra cost to you.

Where to Buy Paving Slabs in the UK

Once you know how many slabs you need, compare prices across these suppliers. For larger patio projects, bulk ordering direct from a builders merchant or paving specialist is often significantly cheaper per slab.

Links marked above are affiliate links — we may earn a small commission at no extra cost to you. We only link to reputable UK suppliers.