Paving Stone Calculator
Calculate how many paving stones you need for a path, patio or outdoor area, based on area, stone size and waste.
How to use the paving stone calculator
- Enter the length and width of the path or area to be paved.
- Enter the stone size (assuming square stones) in centimeters.
- Enter your desired waste — 10 % is common, more for complex shapes or many cuts.
How the stone count is calculated
The calculator adds waste to the area, then divides by the area of one stone:
A straight path with simple cuts needs less waste than a path with curves or many corners.
Fall and drainage — what the calculator does not cover
The number of slabs is the easy part of the job. What decides whether the paving still looks good in five years is what lies underneath it, and which way the water runs. Slabs laid perfectly level against a house wall channel rainwater towards the foundation instead of away from it. Paving is therefore normally laid with a slight fall away from the building — on the order of one centimetre per metre, enough for water to run off without the slope being uncomfortable to walk on.
Beneath the slabs sits a compacted sub-base of crushed stone and a thin bedding layer of sand. The sub-base spreads the load and stops frost from lifting individual slabs unevenly through winter, which is why paving in climates with ground frost generally requires more excavation than in milder regions. This calculator covers the slabs only — crushed stone, sand and any edge restraint must be worked out separately.
Frequently asked questions
Do I need a gravel base under the paving stones?
Yes, most paving stones should be laid on a compacted gravel or crushed-stone base of at least 5–10 cm to prevent settling and ensure good drainage.
How wide a joint should I plan between the stones?
A 1–2 cm joint is common. If the joints are wide, it can be worth increasing the area somewhat beyond the stones' own dimensions, since the joint sand also takes up space.