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Post Hole Concrete Calculator

Estimate concrete volume needed for round post holes from diameter, depth, and hole count.

Updated April 17, 2026
Free online tool
Planning and research use

Why this page exists

Fence and post projects are easier to plan when each hole’s concrete volume is turned into a full materials estimate instead of being guessed from the bag count alone. This calculator helps visitors estimate concrete needed for round post holes from hole diameter, depth, and the number of holes in the project.

Interactive tool

Run the estimate

Enter your numbers and read the result first, then use the sections below to understand what affects the outcome.

Calculator

Post hole concrete calculator

Estimate concrete needed for round post holes using diameter, depth, and hole count.

Result

18.85 cu ft

Estimated concrete volume for round post holes from cylinder volume multiplied by the number of holes entered.

Concrete volume per hole2.36 cu ft

Total concrete volume18.85 cu ft

Number of holes used8

Total concrete in cubic yards0.698 cu yd

A 12.0 inch round hole at 36.0 inches deep uses about 2.36 cubic feet of concrete per hole in this simple cylinder estimate.
8 holes brings the total to about 18.85 cubic feet, or roughly 0.698 cubic yards.
Use the result as a materials estimate only, because gravel bases, flare-outs, and code-driven footing shapes can change the real volume needed.

This is a basic cylindrical-volume estimate only. Gravel bases, bell-shaped holes, overfill, and local code requirements can change the actual amount of concrete needed.

Planning note

Last updated April 17, 2026. Use this tool to compare scenarios and plan ahead, then confirm important details with the lender, employer, insurer, contractor, or other qualified provider involved in the final decision.

How it works

What the calculator is doing

Enter the hole diameter, hole depth, and number of holes.

The calculator uses cylinder volume math to estimate concrete volume per hole.

It multiplies that per-hole amount by the total number of holes and shows the result in cubic feet and cubic yards.

Understanding your result

This is a practical cylinder-based estimate only. Gravel bases, bell-shaped footings, overfill, and local code requirements can change the real concrete amount needed.

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Examples

Ways people use this tool

Example scenarios help turn a quick estimate into a more useful comparison or planning step.

Estimate concrete for a fence-post run

A quick volume estimate can help determine whether the project needs a few bags or a much larger order.

Compare hole sizes before digging

Changing diameter or depth makes it easier to see how much extra concrete a larger footing will require.

Use it with bag and fence tools

Post-hole volume becomes more useful when paired with cement-bag and fence-layout tools.

When to use it

Good times to run this calculator

Use this when you want a quick concrete estimate for round post holes before buying bags or scheduling delivery.

It is especially useful for fence, deck, sign-post, and other projects where several similar holes are planned.

Assumptions and limitations

The estimate assumes each hole is close to a round cylinder with the diameter and depth entered.

It does not account for gravel bases, flare-outs, irregular shapes, or engineered footing requirements.

Common mistakes

Avoid the usual input mistakes

Forgetting to convert a larger number of holes into total volume can make a project look much smaller than it really is.

Using nominal hole size instead of actual planned diameter and depth can skew the concrete estimate quickly.

Practical tips

Measure one representative hole size carefully before ordering concrete for the whole project.

Use the cubic-feet result with a cement-bag tool if you want to translate the volume into bag count next.

Worked example

Walk through a realistic scenario

A worked example shows how the estimate behaves when the inputs resemble a real planning decision.

Estimate total concrete for multiple post holes

A project needs 8 round holes, each 12 inches wide and 36 inches deep, and the builder wants to estimate total concrete volume.

1. Enter the hole diameter and depth.

2. Estimate the cylinder volume for one hole.

3. Multiply that per-hole amount by the number of holes.

Takeaway: The result gives a cleaner materials checkpoint than guessing bag count from the number of posts alone.

FAQ

Common questions

How is concrete volume estimated here?

The calculator treats each hole as a cylinder, estimates the volume per hole, and then multiplies by the number of holes entered.

Why might actual concrete use differ from the estimate?

Because real holes can include gravel bases, wider bottoms, extra overfill, or local code details that change the finished shape.

Why show cubic yards too?

Because cubic feet is useful for smaller jobs, while cubic yards can be easier to use when the total volume gets larger.

Related tools

Keep comparing

Concrete, fence-post, cement-bag, and privacy-fence tools help turn the volume estimate into a fuller materials plan.

Gravel and fence-gate tools add context when the post holes are only one part of a wider fence project.

Home ToolsUpdated April 11, 2026