How the calculation works
Net concrete = count × fill depth × (round hole area − embedded post area).
A worked example
Three 12 in holes, each 2 ft deep, total 4.7124 ft³. Three actual 4 × 4 in posts displace 0.6667 ft³ of that volume.
Does the calculator subtract the post?
Yes. It subtracts the embedded square or round post volume from the round hole volume before applying your allowance. Use the actual measured post size and only the depth that will contain concrete.
What to check before using the result
- Enter concrete fill depth only; any gravel bottom is separate.
- Hole depth, diameter and setting method must come from the project requirements.
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References & product information
Method prepared 2026-10-21. See our calculation and editorial methods. Spotted a problem? Tell us about it.