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Post Hole Gravel Calculator

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

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

Why this page exists

Post-setting projects get easier to plan when gravel depth and hole size are turned into a total material estimate instead of being guessed at the supply yard. This calculator helps visitors estimate gravel needed for round post holes from hole diameter, gravel depth per hole, 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 gravel calculator

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

Result

3.93 cu ft

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

Gravel volume per hole0.39 cu ft

Total gravel volume3.93 cu ft

Hole count used10

Total gravel in cubic yards0.145 cu yd

A 12.0 inch round hole with 6.0 inches of gravel uses about 0.39 cubic feet of gravel per hole in this simple cylinder estimate.
10 holes brings the total to about 3.93 cubic feet, or roughly 0.145 cubic yards of gravel.
Use the result as a planning estimate only, because drainage choices, compaction, and irregular hole shapes can change the real gravel need.

This is a basic cylindrical-volume estimate only. Real gravel needs can still vary with soil conditions, hole shape, compaction, and drainage details.

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 hole diameter, gravel depth per hole, and the total number of holes.

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

It multiplies the per-hole amount by the hole count and shows the total in cubic feet and cubic yards.

Understanding your result

This is a practical cylinder-based estimate only. Actual gravel needs can still change with soil conditions, compaction, drainage choices, and whether the finished hole shape differs from a simple round cylinder.

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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 gravel for a fence-post run

A quick per-hole and total-gravel estimate can help determine whether a project needs a few bags or a larger bulk order.

Compare a shallow base with a deeper base

Changing gravel depth per hole makes it easier to see how drainage allowance affects total material needs.

Use it with post-hole concrete tools

Gravel planning becomes more useful when reviewed beside post-hole concrete and fence-layout tools.

When to use it

Good times to run this calculator

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

It is especially useful for fence, deck, sign-post, and similar projects where several holes will use the same gravel base depth.

Assumptions and limitations

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

It does not account for irregular bottoms, compaction loss, flare-outs, or unusual drainage assemblies.

Common mistakes

Avoid the usual input mistakes

Using full hole depth instead of just the gravel depth can overstate the gravel estimate quickly.

Forgetting to multiply by the full hole count can make the project look much smaller than it really is.

Practical tips

Measure one representative hole carefully before ordering material for the entire project.

Review the total in cubic yards if you are comparing a bagged purchase with a bulk gravel delivery option.

Worked example

Walk through a realistic scenario

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

Estimate gravel for multiple post holes

A homeowner wants a quick gravel-base estimate for a run of round post holes before buying base material.

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

2. Estimate the gravel volume for one hole.

3. Multiply the per-hole volume by the total number of holes.

Takeaway: The result turns one gravel-base assumption into a cleaner total-material estimate for the full post project.

FAQ

Common questions

How is gravel volume estimated here?

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

Why might actual gravel use differ from the estimate?

Because real holes can vary in shape, drainage design, compaction, or bottom profile, which can change the final gravel amount needed.

Why show cubic yards too?

Cubic feet is useful for smaller jobs, while cubic yards can be easier to use when comparing larger gravel orders or delivery quantities.

Related tools

Keep comparing

Post-hole-concrete, fence-post, gravel, and retaining-wall-gravel tools help place the gravel-base estimate inside a fuller footing and site-material workflow.

Gravel-delivery and privacy-fence tools add context when the next question is how to source the material and connect it to the broader fence layout.

Home ToolsUpdated April 17, 2026