For calculating the quantity of cement, sand, aggregate, and water follow these steps:

For one cubic meter of M20 (1:1.5:3)

Wet volume of Concrete = 1 cum

Dry volume of Concrete = 1.54 cum (increased by 54% for dry volume)

Cement = 1.54/(1+1.5+3) × 28.8 = 8.064 say 8 bags. (1 cum = 28.8 bags)

Sand = 1.54/(1+1.5+3) × 1.5 = 0.42 cum or 14.83 cft.

Aggregate = 1.54/(1+1.5+3) × 3 = 0.84 cum or 29.66 cft.

Water Quantity

Assume water-cement ratio = 0.5

Water required = water-cement ratio × Cement quantity (kg)

= 0.5 × 400

= 200 litres.