How this calculator works
Measure depth after levelling the soil. The default 1800 kg/m3 is a supplier example for clean stone, not a universal density for decorative rock. A circle uses its diameter and a triangle needs its perpendicular height.
Formula
A = L x W, pi x D^2 / 4, b x h / 2, or (front + back) x h / 2; Vnet = A x depth; Vorder = Vnet x (1 + waste); mass = Vorder x density; cost = tonnes x rate or Vorder x rate, plus fixed charges.
Worked example
A 5 m by 4 m bed at 0.1 m deep holds 2 m3. At 1800 kg/m3 and 10% waste, order 2.2 m3 or 3960 kg.
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Frequently asked questions
Will large cobbles cover the same area as small chips?
Not always. Void space and the number of particle layers affect coverage. Obtain the bulk density and recommended depth for the exact product.
Can I measure a curved bed?
Split it into simple shapes and add the separate results. Circular mode assumes a full disk.
Does waste account for settling?
Waste is an extra ordering allowance. This page does not predict settlement or choose a planting-bed depth.