Post Hole Concrete Calculator
Use this concrete-focused post-hole tool after post locations are established; it returns cubic feet, cubic yards, and approximate bag quantity.
Compare up to three scenarios
Capture the current result, change one or more inputs, and see the options side by side. The first option becomes your baseline.
Your live calculator remains unchanged. Capture it only when you want a comparison point.
Save this estimate as a project section
Name rooms, roof planes, yard areas or other sections separately. CalcurHome will combine compatible results from this calculator on this device.
No account or personal information required. Data remains in this browser until you delete it or clear browser storage.
View all saved project estimatesWhat does the post hole concrete calculator calculate?
Find each hole’s cylindrical volume, subtract the embedded round-post volume, multiply by the hole count, and add placement waste. This page owns post-hole concrete and bag quantity; use the Fence Post Spacing Calculator first when the unresolved task is post count or layout.
Concrete around round posts
The formula subtracts a round post cylinder from each round hole cylinder. Dimensions are converted to feet before volume is calculated, so the result is cubic feet and can then be converted to bags or yards.
How to measure for an accurate estimate
- Measure hole diameter across the widest point and depth from finished grade to the bottom.
- Check several holes because augers and loose soil rarely produce identical cylinders.
- Enter the embedded diameter of a round post, or zero to ignore displacement.
- Calculate bell-shaped bases, footings, or rectangular posts separately for a closer estimate.
Eight fence posts
Eight 12-inch-diameter holes are 3 ft deep around 4-inch round posts, with 10% extra.
Net volume is 16.76 cu ft; with extra it is 18.43 cu ft, or about 31 80-lb bags.Before you purchase material
- Call the required utility-location service before digging and respect marked exclusion zones.
- Confirm post depth, diameter, frost, drainage, uplift, and inspection rules locally.
- Keep bagged mix dry and compare total mixing effort with a small ready-mix delivery.
- Brace posts before placement and follow the concrete and post manufacturers’ curing guidance.
Common questions
How many bags of concrete do I need per fence post?
A 12-inch-diameter, 3-foot-deep cylindrical hole around a 4-inch round post uses about 2.10 cubic feet before waste, or roughly four 80-pound bags at 0.60 cubic foot each. Actual irregular holes may use more.
Should I subtract the fence post from the hole volume?
Yes, for a tighter material estimate, subtract the embedded post volume. The difference is most noticeable with large posts or many holes. For irregular or rectangular posts, the calculator’s round-post assumption is approximate, so retain a practical allowance.
How deep should a post hole be?
Depth depends on fence or deck loads, post height, soil, frost depth, wind, uplift, and local code. Do not choose depth from a concrete estimate. Follow approved plans, manufacturer instructions, and requirements from the local building authority.
Can I pour dry concrete mix into a post hole?
Only use a dry-placement method if the specific manufacturer expressly permits it and follow its water and installation directions. Conventional mixing generally provides better control. Structural posts need the specified concrete quality, consolidation, positioning, and curing.
Sources and reference standards
- QUIKRETE Concrete Mix Product DataManufacturer product data used to cross-check typical bag yields; verify the yield printed on the bag you buy.
- International Code Council — 2024 International Residential CodePrimary model-code source for residential foundations, reinforcement, masonry, and stair safety requirements.
See every citation and the calculators that use it in the calculator source index.
Use this result in a complete project plan
Fence planning guide
Fence quantity depends on layout, not perimeter alone. Corners, ends, gates, grade changes and fixed panel widths affect posts and sections, while post-hole concrete and cost belong to later stages. This guide preserves the layout decisions behind every purchase line.
Did this calculator help you make the next project decision?