Concrete @ your Fingertips

Estimating the quantity of dry-blended concrete

When concrete is to be mixed on site rather than ordered from a ready-mixed concrete supplier, an estimate of the materials requirement is necessary. The concrete can be purchased in bags already proportioned as dry-blended cement/sand/aggregate.

Concrete in dry-blended bags for the DIY market will have printed advice on the bag stating the volume of concrete it will provide when water is added. Generally dry-blended concrete is sold in 25kg bags. By dividing the estimated concrete volume needed for a project by the stated volume the required number of bags for the project can be determined


The estimated concrete volume for driveway slab = 1.65 m3
Using 25 kg bags of dry-blended concrete (each producing say 0.010 m3 of concrete)
Number of bags needed = 1.65 / 0.010 = 160.6 = 165

Acknowledgement: The Concrete Society