Concrete Calculator
Concrete volume and cement bags for slabs, footings and columns
About Concrete Calculator
The concrete calculator answers “how much concrete do I need” for the shapes that come up on real jobs: slabs, footings and beams, round and square columns, circular slabs or tubes, curb-and-gutter runs, and even stairs — either solid stepped or a waist slab with treads. Enter the dimensions and quantity of identical elements, and it returns the volume.
Two volumes are reported: the net geometric volume and the volume including a 5% safety factor, which covers spillage, over-excavation, and uneven subgrade. The tool also converts volume into 25 kg cement bags using an adjustable rate — the default of 13 bags per m³ suits a typical 1:2:3 cement-sand-aggregate mix.
Use it before calling the ready-mix plant or working out how many bags to haul for a DIY pour. Everything computes live in your browser, free. The bag rate is an assumption, not a specification — adjust it to your actual mix design, and remember that quantities are estimates.
How to use Concrete Calculator
- Pick the element shape: slab, footing or beam, round or square column, tube, curb and gutter, or stairs.
- Enter the dimensions the shape asks for — lengths and heights in meters, slab thickness in centimeters.
- Set the quantity if you are pouring several identical elements.
- Adjust the cement bags-per-m³ rate to match your mix if needed.
- Read the net volume, the volume with the 5% safety factor, and the number of 25 kg cement bags.