About cement calculator
A concrete mix is described by its grade, such as M20, which means a strength of 20 N/mm² after 28 days. The calculator turns slab size and grade into cement bags, sand and aggregate.
Nominal mixes by grade
- M15 is 1 : 2 : 4 (cement : sand : aggregate).
- M20 is 1 : 1.5 : 3.
- M25 is 1 : 1 : 2.
Method
Dry volume is about 1.54 times the wet volume. Divide by the sum of the ratio parts and multiply by each part. One bag of cement is 50 kg, or about 0.035 m³.
Engineering advice
Structural work such as columns and beams must be designed by a qualified engineer. Treat this tool as a rough estimate for planning.
Always add a margin
These are planning estimates. Real quantities depend on site conditions, brands and wastage, so confirm with your contractor or supplier before ordering.
