Concrete Slab Calculator
Calculate the volume of concrete needed for a slab and how many 20 kg bags you need.
How to use this tool
- Enter slab length, slab width and slab thickness in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your concrete volume and the full breakdown beneath it.
Calculate how much concrete you need for a slab, path, or pad.
Frequently asked questions
- How many bags of concrete do I need for a slab?
- Calculate volume in m³ = length × width × thickness (m). A 20 kg bag covers about 0.01 m³, so divide your volume by 0.01 and round up.