Concrete Calculator

Calculate how much concrete you need for slabs, footings, columns and walls in cubic yards or metres.

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How to Use This Calculator

How to Use

  1. Select the shape of your pour (slab, footing, wall or column).
  2. Enter the dimensions in your preferred units.
  3. Adjust the waste percentage – 10% is standard for most projects.
  4. Read your concrete volume in cubic yards/metres plus estimated bag counts.

Tips

  • For slabs, a typical depth is 4 inches (100 mm).
  • Footings are usually 12 inches (300 mm) deep and at least 12 inches wide.
  • Always round up when ordering – running short is far more expensive than over-ordering.

Common Questions

How much concrete do I need for a 10x10 slab?

A 10 ft × 10 ft slab at 4 inches deep needs about 1.24 cubic yards of concrete, or roughly 1.36 cubic yards with 10% waste.

How many bags of concrete make a cubic yard?

About 60 standard 60 lb bags or 45 standard 80 lb bags make one cubic yard.

Should I add extra for waste?

Yes – 5-10% for simple slabs and up to 15% for irregular shapes or footings with forms.

How thick should a concrete slab be?

A typical garden or shed slab is 100 mm (4 in); driveways and areas taking vehicles usually need 150 mm (6 in) with reinforcement.

Is it cheaper to mix concrete myself or buy ready-mix?

For small jobs bagged or site-mixed concrete is usually cheaper; for more than about a cubic metre, ready-mix delivery is often better value and faster.

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