Project guide
Concrete for Multiple Post Holes
Group identical holes and keep different sizes visible before calculating an order.
Your measurements
Changing units changes the display, not the stored measurement.
Results
Example inputs
Your result will appear here
Enter the measurements and product details, then calculate.
These tools estimate material quantities from dimensions you choose. They do not specify structural depth or load capacity.
Make a group for each geometry
Record hole diameter, round-post diameter, filled depth and count. The form accepts diameters and converts them to radii for the formula. Holes can share a group only when those dimensions agree. A different corner post or deeper section needs its own measurements.
This model represents cylindrical holes and round posts over the entered depth. It does not choose hole spacing or depth and does not model a square post by pretending its side is a diameter.
Example: two groups of holes
For Group A, enter four holes with a 0.30 m hole diameter, 0.10 m post diameter and 0.6 m depth. The radii are 0.15 m and 0.05 m, giving approximately 0.1507964474 m³. For Group B, enter two holes with a 0.40 m hole diameter, 0.10 m post diameter and 0.7 m depth. The radii are 0.20 m and 0.05 m, giving approximately 0.1649336143 m³.
Together they require approximately 0.3157300617 m³ before allowance. A chosen 10% allowance gives approximately 0.3473030679 m³.
Round the combined purchase, not every hole
With an illustrative yield of 0.012 m³ per bag, the combined example requires 29 bags. Keep the unrounded group volumes until this purchasing step. Rounding every hole to whole bags first can overstate a single shared order.
Review the geometry and the specification
A post diameter equal to or larger than its hole diameter is rejected. A radius accidentally entered in a diameter field changes the result substantially. Check the labelled drawing and compare each group with the project specification.
The resulting list is a material calculation. It does not establish the footing size or structural capacity of a fence, deck or other structure.
Frequently asked questions
Can I combine different hole sizes?
You can add their unrounded concrete requirements when the material purchasing specification matches. Keep the different dimensions in separate source groups.
Sources and method
- PackLedge quantity methods
Original derivations using geometry, ratios, sums and whole-package rounding. Each calculator explains its assumptions and worked examples.
- NIST Guide to the SI — Conversion Factors ↗
Reference for unit conversions and clear identification of metric and customary units. Exact base-unit definitions are retained in calculations rather than rounded display factors.
- Your selected product label or technical sheet
The source for the coverage, mixed yield, density, package capacity, sheet dimensions or wallpaper repeat that you enter.