The question should be framed thus: "How to calculate
quantity of steel for practical purpose of construction"....
"In a given RCC design" it is simple to arrive at the
quantity by calculating the lenght of each bar & multiply
with the unit weight of given dia.
The thumb rule for calculating steel quantity is 1.5 to 2.0
Kg/Sft....

For all pratical purpose you can calculate steel by
measurment given by drg.All sreels come with their unit
weight. by calculating their respective unit weight toal
wt. can be calculated.

The quantity of steel can be calculated by formula:
d*d/162 kg/m. where d=diameter of bar in metre
this formula has been derived by relation
density=mass/volume
However, percentage of steel in rcc structure can be taken
as 0.15% of the gross area of cocrete

FOR FOUNDATION 50KG PER CUM
FOR SLAB 80KG PER CUM
FOR BEAM 110 KG PER CUM
FOR COLUMN 160KG PER PER CUM
FOR WALL 80 KG PER CUM
FOR SHELVES 80KG PER CUM
FOR STAIR CASE 100 KG PER CUM

for all practical purposes calculation of steel should be find in bar bending schedule which we can easily understand that which types of bars used and the weight different for all steel dia.