Stone carpet calculator
Natural stone and PU binder for a stone carpet by area, layer thickness and ratio
How the calculation works
Enter the area, choose the layer thickness, the binder-to-stone ratio and the reserve. The calculator works out the weight of natural stone, the number of 25 kg bags, and the polyurethane (PU) binder, rounded up to packs of 20, 5 and 1 kg.
Formula and assumptions
Stone (kg) = area × 15 kg/m² per cm × thickness (cm) × (1 + reserve ÷ 100). Bags = stone ÷ 25, rounded up. Binder (kg) = stone ÷ N for a 1:N ratio. The binder is rounded up to whole kilograms and combined from 20, 5 and 1 kg packs; when only 1 kg is missing to a larger pack, the larger pack is used.
Worked example
Area 10 m², layer 10 mm, ratio 1:15, no reserve: stone = 10 × 15 × 1 = 150 kg = 6 bags of 25 kg. Binder = 150 ÷ 15 = 10 kg = 2 × 5 kg. With a 5 % reserve: stone 157.5 kg → 7 bags; binder 10.5 kg → 11 kg = 2 × 5 kg + 1 × 1 kg.
What affects real consumption
- Layer thickness: every extra millimetre adds 1.5 kg of stone per m².
- Ratio: 1:10 uses more binder than 1:20.
- Edges, stairs, an uneven substrate and grain size change the real consumption.
Frequently asked questions
Is 15 kg of stone per m² per cm exact for every stone?
It is the calculator's working norm; actual consumption depends on grain size and how the mix is laid, so check the manufacturer's data sheet.
Does the calculator work out the price?
No, it only calculates the quantities of stone and binder; the price depends on the supplier and the product.