Concrete Calculator | Slab Volume and Bag Estimate
Calculate concrete volume in cubic meters and estimate 25 kg or 40 kg bag counts from length, width, depth, and waste percentage.
Concrete Volume Estimate
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Calculate Concrete Volume for a Slab
Enter length, width, depth, and waste allowance to estimate concrete volume and approximate bag counts for small slabs, pads, and footings.
Depth and Waste Change the Order Size
Uneven ground, reinforcement, formwork, spillage, compaction, and supplier bag yield can change real material needs. Round up when ordering for a project.
About This Tool
Concrete Calculator estimates the volume of concrete needed for a slab, footing, column, or staircase from entered dimensions. It helps avoid ordering too little material or wasting money on excess.
When to Use It
Use this before ordering ready-mix concrete for a driveway, patio, foundation slab, or fence post footings to determine exactly how many cubic metres to request from the supplier.
How to Use
- Select the shape: slab, footing, column, or staircase.
- Enter the required dimensions.
- Click Calculate to see the volume in cubic metres and cubic feet.
- Add 5 to 10 percent for waste when ordering.
Frequently Asked Questions
How much extra should I order for wastage?
Add 5 to 10 percent to the calculated volume when ordering to account for spillage, uneven subgrade, and form imperfections.
What is the standard concrete thickness for a driveway?
Residential driveways typically use a 100 mm slab. For heavy vehicles, 150 mm provides better durability.
When is ready-mix better than bagged concrete?
For pours larger than about 1 cubic metre, ready-mix is more economical and consistent. Bagged mix is practical for smaller DIY jobs.