BuildCalcs Paving Slab Calculator
Estimate the number of paving slabs required for a rectangular patio or path.
How the paving calculation works
The calculator divides the total paved area by the face area of one slab, applies the waste allowance and rounds up to a whole slab.
Allowing for joints
This simple purchasing estimate does not subtract joint area. In practice the waste allowance, cuts and layout have a larger effect on how many whole slabs you should order.
Frequently asked questions
Can I use this for a path?
Yes. Use the total path length and width, or split irregular paths into rectangular sections and add the results.
What about mixed-size patio packs?
Use the manufacturer's stated pack coverage instead of a single-slab count when a pack contains several slab sizes.
Related groundworks calculator
Planning a concrete base or footing as part of the same project? Use the Concrete Calculator UK to work out cubic metres, litres and bag-yield quantities.
Planning a paving slab order
The calculator compares the patio or path area with the face area of the selected slab and then adds the chosen waste allowance. This gives a useful whole-slab purchasing estimate for a regular rectangular layout. Enter the actual slab dimensions from the product specification, particularly where a marketed nominal size differs from the manufactured size.
Joints and laying patterns affect the result
A simple area calculation cannot reproduce every joint width or modular pattern. With large slabs, regular joints may slightly change the exact number of units across a run. Mixed-size patio packs, circles and random patterns should instead be planned using the manufacturer's layout or pack coverage information.
Where extra slabs are useful
Edges, diagonal cuts, steps, drain covers and curves can create offcuts that cannot be reused elsewhere. An allowance also gives some protection against breakage and future replacement, especially for products that may later be discontinued or change shade. Bedding material, sub-base, jointing compound and edge restraints are separate quantities and are not included by this slab calculator.