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.