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River Rock Bed & Allowance Budget Calculator

Estimate decorative rock volume, mass and spending with an added allowance.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Edit a calculated value to solve backwards, or lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A 5 by 4 meter bed at 10 centimeters deep needs 2 m³ before allowance. At 10% extra, a custom density of 1,900 kg/m³ and 25 per tonne, the order is 4.18 tonnes costing 104.50.

Order volume = length × width × depth × (1 + allowance); cost = volume × bulk density × mass price

Worked example

Enter these known values and leave the other values blank.

Rock type
Custom
Density
1900 kg/m³
Length
5 m
Width
4 m
Depth
10 cm
Wastage
10 %
Price per one unit of mass
25 USD / t
Area
20 m²
Volume
2 m³
Volume needed
2.2 m³
Weight needed
4.18 t
Price per one unit of volume
47.5 USD / m³
Total cost
104.5 USD

Assumptions and limitations

  • The entered bulk density should account for the delivered rock and its void spaces. Solid-rock density is unsuitable for a loose bed unless adjusted. Depth is modeled uniformly; irregular surfaces and supplier minimums need separate allowances.
  • Enter dimensions, densities and prices that describe the actual project. Quantities absent from the formula are not added automatically.

Common questions

Does this model account for spaces between rocks?

The entered bulk density should account for the delivered rock and its void spaces. Solid-rock density is unsuitable for a loose bed unless adjusted. Depth is modeled uniformly; irregular surfaces and supplier minimums need separate allowances.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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