Concrete Calculator

Calculate how much concrete you need for a slab, path, or foundation. Volume and bag estimates.

Dimensions

Your Results

Volume-- m³
Bags (25kg)--
Bags (40kg)--

~60 x 25kg or ~40 x 40kg bags per m³. Buy 10% extra.

What is a Concrete Calculator?

A concrete calculator helps you estimate the volume of concrete needed for a project—whether a patio slab, driveway, path, or foundation. It converts dimensions into cubic metres (or cubic yards) and estimates the number of bags required.

The Formula

Volume = Length × Width × Depth

  • Metric: Length (m) × Width (m) × Depth (cm ÷ 100) = m³
  • Imperial: (Length × Width × Depth in inches) ÷ 46656 = yd³ (or ÷ 27 for depth in feet)

Bag Estimates

  • 25 kg bags: Approximately 60 bags per cubic metre
  • 40 kg bags: Approximately 40 bags per cubic metre

These are estimates; check the coverage on your specific product.

Example

  • Slab: 5m × 3m × 10cm
  • Volume: 5 × 3 × 0.10 = 1.5 m³
  • Bags (25kg): ~90 bags
  • Bags (40kg): ~60 bags

How Our Calculator Works

  1. Enter dimensions: Length, width, depth
  2. Choose units: Metric (m, cm) or Imperial (ft, in)
  3. Get results: Volume and bag estimates

Frequently Asked Questions

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

For 4 inches thick: (10 × 10 × 0.33) ÷ 27 ≈ 1.2 cubic yards. For 10cm: 10m × 10m × 0.10m = 10 m³.

Should I buy extra?

Yes. Buy 5-10% extra for wastage, uneven ground, and spillage.

What depth for a driveway?

Typically 4-6 inches (10-15 cm) for cars. Heavier vehicles need more.

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