/// Answer-first planning notes
How much concrete fills the space around my posts?
| Planning input | Calculation role | Field check |
|---|---|---|
| Hole and post diameters | Create the annular cross-section | Measure actual geometry |
| Depth and hole count | Scale concrete volume | Group matching holes only |
| Bag yield and waste | Create a whole-package estimate | Use the named product value |
Metric and imperial annular volumes derive from the exact international-foot definition, without adding a footing-design assumption.
Evidence: National Institute of Standards and Technology/// Formula & field notes
How this post hole concrete estimate works
FormulaNet concrete = holes × π × ((hole diameter ÷ 2)² − (post diameter ÷ 2)²) × depth. Apply waste, divide by bag yield, and round up.
Worked example
Four 12 in diameter holes around 4 in posts at 3 ft deep contain about 8.3776 ft³; with 10% waste and 0.60 ft³ per bag, order 16 bags.
/// Source trail
Data & assumptions
Every source has a declared scope. A reference can support a conversion or product assumption without turning this estimate into a supplier quote.
Exact international-foot to meter conversion; U.S. survey-foot conversion is explicitly outside this claim.
Effective 2025-08-18 · Reviewed 2026-07-15 · Next review 2027-07-15Independent confirmation that one international foot equals exactly 0.3048 meters; U.S. survey-foot conversion remains distinct.
Effective 2025-06-10 · Reviewed 2026-07-15 · Next review 2027-07-15/// Common questions
Post Hole Concrete calculator FAQ
What should I verify before ordering post-hole concrete?
Confirm field dimensions and approved hole geometry, post diameter, and selected bag yield against the exact product or supplier information. ProjectQty shows the assumptions so you can replace planning defaults before ordering whole bags.
How does waste affect the post-hole concrete estimate?
Waste is applied after the base geometry is calculated and before discrete packages or pieces are rounded up. Use a higher allowance for complex layouts, cuts, pattern matching, breakage, or uncertain field dimensions.
Is this post-hole concrete result a professional design?
No. It is a quantity-planning result. This quantity estimate cannot select hole depth, foundation geometry, wind resistance, frost protection, or code requirements.