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Post Hole Volume & Order Calculator

Calculate cylindrical or rectangular hole volume and an ordering 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 rectangular hole 50 × 50 centimeters and 1 meter deep has a volume of 0.25 m³. Two such holes with a 10% ordering allowance require 0.55 m³ before subtracting anything inside the holes.

Cylinder volume = π × radius² × depth; rectangular volume = length × width × depth; order = hole volume × quantity × (1 + allowance)

Worked example

Enter these known values and leave the other values blank.

Depth
100 cm
Length
50 cm
Width
50 cm
Quantity of posts
2 units
Waste
10 %
Volume
0.25 m³
Required concrete (rectangular hole)
0.55 m³

Assumptions and limitations

  • No. It uses the entire hole volume. Posts, forms and other displaced volumes require adjustment if you need the net material volume. This geometry model does not determine foundation dimensions or structural suitability.
  • Use consistent units and project-specific dimensions, density and prices. This geometric estimate does not add quantities that are absent from the formula.

Common questions

Does the result subtract the post’s volume?

No. It uses the entire hole volume. Posts, forms and other displaced volumes require adjustment if you need the net material volume. This geometry model does not determine foundation dimensions or structural suitability.

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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