How to use this fence post concrete calculator
Concrete volume is the space inside the cylindrical hole minus the part occupied by the post. This tool uses the buried portion of a square post and lets you enter the specific dry-mix bag yield printed by the manufacturer.
Step-by-step instructions
- Measure the hole diameter and effective filled depth in inches.
- Enter the buried post width and number of holes.
- Set bag yield and waste allowance to obtain an estimated order quantity.
Calculation formula
Important assumptions and limitations
Circular holes, square posts, constant cross-section, and concrete to the entered fill depth. Gravel below the concrete, tapered holes, bells and unused top depth must be accounted for by adjusting inputs.
For material orders, confirm package yields, stock sizes and installation instructions with the actual manufacturer or supplier. Your building department determines the applicable local code; a quantity estimator is not a structural design or permit approval.
Frequently asked questions
How much concrete does a 50 lb bag make?
This calculator defaults to 0.375 cubic feet as an example. Always use the yield shown for your specific brand and product.
How deep should fence posts be?
The required depth depends on height, soil, frost line, wind loading and local rules. This tool estimates materials, not a safe footing design.
We publish formulas and assumptions so you can verify an estimate. Learn about our methodology or report an issue.