Measurements, formulas and worked examples
Check the calculation, see how post displacement and bag yield change the result, and understand the limits.
Material quantities · US units
Post hole concrete calculator
Estimate concrete volume and whole bags for round post holes. Subtract the square or round post, include multiple holes, and choose your own mix yield and allowance.
Material quantities · US units
Result
Net volume = round-hole volume − post displacement. Bag count = combined volume with your allowance ÷ yield per bag, rounded up.
How to use this estimate
Enter dimensions already chosen for your project. Use the actual post size and only the length inside the concrete. The result shows net cubic feet, total with your allowance, cubic yards, liters and whole bags. It remains available without a product match or purchase. This estimates materials; it does not determine safe footing dimensions, load capacity, frost depth or excavation requirements. Contact 811 before digging and follow your local notification process.
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