When to use this calculator
Estimate concrete around cylindrical posts in round holes. Assumes the round post occupies the full concrete depth. Irregular holes and bases are excluded.
Explore the material quantities calculators for other questions in this topic. For a related calculation, use the Rafter Length Calculator: Estimate common-rafter slope length from a roof span, rise and overhang.
PUTTING IT INTO PRACTICE
Post Hole Concrete: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Hole diameter (m) | 0.3 |
| Hole depth (m) | 0.6 |
| Round post diameter (m) | 0.1 |
| Holes (integer) | 10 |
| Result | 0.376991 m³ |
- Check the input labels and enter the example values above.
- Apply the relationship: Concrete volume = π(hole radius² − post radius²) × depth × count.
- The result is 0.376991 m³, rounded for display.
How to interpret your result
Assumes the round post occupies the full concrete depth. Irregular holes and bases are excluded.
Calculate net geometric quantities first, then apply a project-specific allowance where appropriate. Coverage per bag or pack should come from the product label. Bulk density, trimming and compaction can substantially change order quantities.
Frequently asked questions
Does a geometric estimate include waste automatically?
Only when a waste or allowance input is provided. Otherwise add an appropriate allowance separately before ordering.
When is the post hole concrete calculator useful?
Estimate concrete around cylindrical posts in round holes. Assumes the round post occupies the full concrete depth. Irregular holes and bases are excluded.
How do I use the post hole concrete calculator?
Enter hole diameter (m), hole depth (m), round post diameter (m), holes (integer). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Concrete volume = π(hole radius² − post radius²) × depth × count.
What should I check before using the result?
Assumes the round post occupies the full concrete depth. Irregular holes and bases are excluded.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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