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Concrete Calculator

For a slab, foundation or path, you first calculate the concrete volume in cubic metres, then how many bags of ready-mix concrete that requires.

m
m
m

Result

1.2 m³

Concrete volume

Bags (25 kg, indicative)
96
How this was calculated
  1. 1Volume: length × width × depth4 × 3 × 0.1 = 1.2 m³

Formula

Volume = length × width × depth

This is a simple volume calculation in metres. To estimate the bag count, the calculator uses the common rule of thumb that a 25kg bag of ready-mix concrete yields about 12.5 litres (0.0125 m³) of mixed product. This varies by brand; check the packaging for the exact yield.

Worked examples

A path 4 × 3 m with a 10 cm depth

→ Volume 1.2 m³, about 96 bags of 25 kg.

Common mistakes

  • Entering the depth in centimetres instead of metres.

Limitations

  • The bag count is an estimate based on a general rule of thumb; the actual yield is on your brand’s packaging.

When to use it

  • Ordering material for a patio, path or foundation.

Frequently asked questions

Should I use ready-mix bags or delivered concrete?

For small jobs, bags are practical; for large volumes (roughly 1 m³ or more), delivered concrete is often cheaper and less work.

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