Fence Post Concrete and Bag Calculator
Calculate concrete around round or square fence posts, including total volume, 80 lb bags, waste, and editable material cost.
How to use the fence post concrete calculator
- Measure the actual project. Break irregular work into separate sections and record finished dimensions consistently.
- Enter the core measurements. The quick view focuses on project geometry; add or subtract sections where the calculator supports multiple areas.
- Review purchasing assumptions. Open Advanced inputs to replace example prices, waste, coverage, density, pack size, minimum order, or delivery assumptions with current project information.
- Calculate and verify. Review the formula, limitations, whole-unit rounding, product instructions, and supplier requirements before purchasing.
Key inputs covered: Post cross-section, Hole diameter, Concrete depth, Post width or diameter, Post holes, Spillage and waste allowance, Concrete yield per bag, Bag example price, Ready-mix example price.
Result coverage: The fence post concrete calculator reports 6 separate quantities so the primary estimate and its supporting purchase or planning values can be checked together.
How the estimate works
Circular hole area minus round or square post area, multiplied by concrete depth and post count, gives volume; allowance is added before bags round up.
For each post, the embedded post volume is deducted from the cylindrical hole before waste and bag rounding.
Assumptions, rounding, and limitations
Dimensions are treated as finished measurements. Only deductions and allowances entered above are included. Decimal measurements display to two places; purchase quantities round up when a whole container or piece is required.
- This estimates concrete quantity only; it does not determine required hole diameter, embedment, footing shape, frost depth, post size, or fence design.
- Soil, wind, fence height, gates, frost, drainage, post material, and local code affect the required foundation.
- Confirm bag yield, hole geometry, bracing, water, placement, curing, and structural requirements before installation.
Sources and review
These references support unit conversions and selected planning assumptions. Product instructions and local requirements control the actual project.
Last reviewed: 2026-10-09
Editorial process
BuildPlanCalc publishes the formula, editable assumptions, limitations, and supporting references so the estimate can be checked rather than treated as a black box. See the calculation and review methodology, or report a correction.
Frequently asked questions
Are the results exact?
No. Results are planning estimates based on the dimensions and assumptions entered. Confirm product coverage, site conditions, and ordering rules with the supplier.