Concrete mix ratios from M5 to M30 and how dry volume is calculated

Nominal mixes from M5 (1:5:10) through M20 (1:1.5:3) up to M25 and M30 remain the fastest way to estimate small and medium works. Above M25, IS 456 expects a design mix backed by trial cubes.

Wet volume is the finished, compacted concrete you can measure in the formwork. Dry ingredients occupy far more space because of voids, so we multiply by 1.54 (some estimators use 1.52–1.57) before splitting by mix ratio.

Cement is then converted by density: one cubic metre of cement weighs about 1440 kg, so a bag of 50 kg is 0.0347 m³. Sand is normally billed at 1550 kg/m³ and coarse aggregate around 1500 kg/m³.

Water is derived from the water-cement ratio. At 0.5, a mix requiring 320 kg of cement needs roughly 160 litres of water, adjusted downward when admixtures or damp aggregate are involved.