Concrete Calculator

Estimate concrete volume, bags and cost for slabs, footings and pads.

Your details

Length(m)

Width(m)

Thickness(cm)

Waste allowance(%)10

025

Price per m³($)

One 40 kg bag of pre-mixed concrete yields roughly 0.018 m³. Ready-mix is normally ordered in quarter-cubic-metre steps.

Formula

volume = length × width × thickness × (1 + waste)

A 6 × 4 m slab at 12 cm needs about 3.17 m³ including 10% waste.

How much waste should I allow?

5–10% for a flat slab, up to 15% for uneven subgrade or complex forms.

Bags or ready-mix?

Bags make sense below about 1 m³. Beyond that, ready-mix is cheaper and far faster.

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