Concrete Calculator

How it works

How to use the concrete calculator

Concrete quantity is length × width × depth. A 3 m × 3 m slab that's 150 mm thick needs 1.35 m³ of wet concrete. Because the dry ingredients pack together when mixed, sites use a dry volume factor of about 1.54 (1.52–1.57) to work out materials, then divide by the mix ratio.

For M20 nominal mix (1 : 1.5 : 3), 1 m³ of concrete needs roughly 8 bags of 50 kg cement, 0.42 m³ of sand and 0.84 m³ of 20 mm aggregate. Results are shown in cubic metres and cubic feet (1 m³ = 35.31 cft), the units Indian material suppliers commonly use, along with approximate water for your water–cement ratio.

Nominal mixes are fine for small works and estimates. For structural concrete, especially M25 and above, IS 456 expects a design mix tested by a lab, and your structural engineer's specification always takes priority over any thumb rule.

1. Choose metres or feet and enter the dimensions.
2. Enter how many identical elements (e.g. footings).
3. Pick the concrete grade and wastage.
4. Read volume, cement bags, sand, aggregate and water.