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Post Hole Concrete Calculator

Estimate the concrete needed to set fence posts, allowing for the volume taken up by the post.

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Enter Hole diameter (cm), Hole depth (cm), Post width (cm), Number of posts and the Post Hole Concrete Calculator works out Concrete per hole, Bags needed (20 kg) straight away. For instance, with Hole diameter (cm) = 30, Hole depth (cm) = 60, Post width (cm) = 10 and Number of posts = 4 it returns Concrete per hole = 36.412 L and Bags needed (20 kg) = 10.

How to use it

  1. Enter your values: Hole diameter (cm), Hole depth (cm), Post width (cm), Number of posts.
  2. Read the result instantly: Concrete per hole, Bags needed (20 kg).

Frequently asked questions

How does the Post Hole Concrete Calculator work?

It takes Hole diameter (cm), Hole depth (cm), Post width (cm) and Number of posts and derives Concrete per hole and Bags needed (20 kg) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

4 values: Hole diameter (cm), Hole depth (cm), Post width (cm) and Number of posts. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Hole diameter (cm) = 30, Hole depth (cm) = 60, Post width (cm) = 10 and Number of posts = 4, the calculator returns Concrete per hole = 36.412 L and Bags needed (20 kg) = 10. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Hole diameter (cm) = 33, Hole depth (cm) = 66, Post width (cm) = 11 and Number of posts = 8 instead, Concrete per hole goes from 36.412 L to 48.464 L — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Hole diameter (cm) = 27, Hole depth (cm) = 54, Post width (cm) = 9 and Number of posts = 2, Concrete per hole comes out at 26.544 L. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Buying the right amount at the merchant: how many tiles, how much paint, how many bags of concrete, and what it all comes to.

What is the most common mistake?

Ordering the exact calculated quantity. Cuts, breakage and pattern matching mean tiles need 10% spare and more on a diagonal layout — and a second batch rarely matches the first for colour.

What is the difference between the Post Hole Concrete Calculator and the Concrete calculator?

This one returns Concrete per hole and Bags needed (20 kg); the Concrete calculator returns Concrete volume (m³) and Approx. weight (kg). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Concrete blocks calculator is the closest one after this: Estimate the number of concrete blocks needed to build a wall.

What else is worth having open alongside it?

Cubic yard calculator and Deck stain calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
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