Landscaping & Boundaries

Fence-post concrete calculator

Estimate concrete volume and bags for a chosen number of circular fence-post holes.

Transparent formulaFormula v1.0 · number of posts × circular hole volume × waste allowance

02Materials estimate

Enter measurements to calculate.

Calculated requirement → waste allowance → recommended order → purchasable units

Volume per hole—

Base concrete volume—

With waste allowance—

Optional bag estimate—

Formula v1.0 · number of posts × circular hole volume × waste allowance · Round purchasable units up to a whole pack, bag or unit where selected.

No account or cloud storage — a saved draft stays in this browser.

Project / reference optional Notes for a merchant optional

Early access

Check supplier pricing

Supplier pricing is being prepared. Create the list first, then use it to ask a local merchant for price, stock, delivery and lead time. No contact details or measurements are sent.

Next steps

Product options · Not connected

Buy what you need

Product options are not connected. Use the calculated list with the product details you choose.

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Get professional quotes

Quote routing is not available. Create a quote-ready materials list to discuss with a merchant.

Scope boundary: Materials volume estimate only — it does not set hole dimensions, post depth, ground treatment, drainage, stability or planning decisions.

Check the path

Your calculation audit

Every total is shown as a short sequence so you can see what was measured, deducted, adjusted and rounded.

01
Awaiting valid measurementsComplete the fields above to reveal the formula path.
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Measure clearly

Simple guidance

Count the post holes you intend to fill, then measure or choose the circular hole diameter and the intended fill depth. Keep the actual hole specification separate from this volume estimate.

Measure the finished surface or internal clear dimensions. Keep a note of any deduction you make.

Worked example

Follow the same logic

Ten circular holes at 300 mm diameter and 600 mm deep contain about 0.424 m³ before a 10% allowance, or about 0.467 m³ after allowance.

Planning tipWrite down the product factor or pack size you used, so a later change is easy to trace.

Before you buy

Three quick checks

01
Count only the holes that will receive the selected concrete or post mix.
02
Use the intended fill depth, not an assumed typical depth.
03
Check the chosen product's bag yield and instructions before ordering.

Quick answers

Useful to know

Why does the hole diameter matter so much?

Each hole is calculated as a cylinder, so volume rises with the square of the diameter. Use the actual chosen diameter rather than a nominal fence-post size.

Does this set the right hole size or post depth?

No. It only estimates concrete volume for dimensions you provide. Ground conditions, frost, drainage, post stability and planning decisions need separate project-specific judgement.

Review record

Transparent calculation method

Last reviewed: 2026-10-17. Formula version: v1.0. Classification: post-hole concrete estimate.

Formula source: src/calculator.js. Uses visitor-entered measurements and product values.

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