Fence Post Concrete Calculator

How much concrete goes around a fence post?

A fence or boundary-wall post footing only needs concrete (PCC) in the gap between the post and the sides of the pit — not the pit’s full volume, since the post itself takes up part of that space. This applies whether you’re setting a precast RCC post, an MS angle post, or a timber post.

How the calculator accounts for post displacement

Whether you’re setting a precast RCC post or an MS angle post, the pit only needs concrete in the space around it, not the full cavity. The calculator finds that space by taking the gross pit volume (cylinder or prism, depending on your pit shape) and subtracting the buried post’s volume over the same depth.

How bag yield (or mix yield) affects the answer

If you’re using pre-mixed bags, yield varies by product, so use the manufacturer’s stated figure where possible. If you’re batching your own PCC — common practice for boundary wall posts — “yield” instead depends on your mix ratio (for example 1:2:4 nominal mix) and how much wet concrete one batch produces. The calculator’s custom yield field accepts either kind of figure; it just needs to be the volume of finished concrete one “unit” (bag or batch) produces.

Whichever you use, the calculator rounds up per hole rather than once for the whole job, so a single post’s footing is never short a partial unit.

Fence run length to post count

If you know your total boundary length but not your post count, enter the run length and your target post spacing (often 3 m for compound walls). The calculator places a post at each end and at every full span, rounding up so the last gap is never longer than your spacing.

Worked example

A 30 m compound wall run with posts every 3 m needs 11 posts. For a 300 mm diameter, 450 mm deep round pit with no gravel base and a 50 mm square (MS angle) post:

• Concrete depth per pit: 450 mm (no gravel base subtracted in this example)
• Concrete needed per pit, with 10% waste: about 30.7 litres
• Total for the run: about 371 litres of PCC

This example doesn’t convert to a bag count, since many installations in India batch PCC on site rather than buying pre-mixed bags — enter your product’s yield, or your own batch’s, in the custom yield field to get a bag or batch count for your specific setup.

Gravel base — optional here

Unlike some markets, many Indian fence and boundary-wall installations pour PCC directly onto compacted soil without a separate gravel layer. The calculator supports one as an optional field — leave it at 0 if your installation doesn’t use one, or set it if you are adding one.

Methodology

What this tool calculates is material quantity — the volume of concrete implied by your hole and post dimensions, converted to a bag or batch count using the yield you enter, plus a waste allowance. Structural adequacy is a separate question: pit depth, diameter, soil, wall height, and post type all affect what a safe installation actually needs, and those are decisions for you or your contractor to confirm locally. Choose suitable pit dimensions first, then use this calculator to plan materials.

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