Post hole concrete calculator
Find the concrete volume surrounding identical round posts.
Formula
V = holes × π/4 × (hole diameter² − post diameter²) × depth × (1+extra/100)
Hole diameter: 12 in · Round post diameter: 4 in · Concrete fill depth: 24 in · Wet yield per bag: 0.4 ft³ · Concrete volume ≈ pi÷4×(0.2032)×((12 in × 0.0254 m/in)+(4 in × 0.0254 m/in))×(24 in × 0.0254 m/in)×(4)×(1+(5)÷100)+0×(0.4507771068) · Cubic feet ≈ (0.1660586615)÷0.3048^3 · Whole bags ≈ ceil(((0.1660586615)×1000÷(0.4 ft³ × 28.31684659 L/ft³))×(1-8.881784197001252e-16))
How to use
- Enter hole and round-post diameters.
- Enter concrete depth, hole count and wet bag yield.
- Set allowance and read volume and whole bags.
Examples
- Two 30 cm holes, 10 cm posts and 50 cm fill depth need 0.0628 m³ before waste.
Frequently asked questions
What depth do I enter?
Only the concrete-filled depth. Exclude gravel; the post is assumed to occupy the full fill depth.
Does it size the footing?
No. Choose dimensions from the project design. A post wider than the hole is rejected.
What about square posts?
This model is for round posts only. Enter zero post diameter for an empty cylindrical hole.
Sources
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