How much steel is required for 1 cum concrete?

depend on the element but mostly (100kg to 160 kg )

It varies from project to project even from element to element depending upon the structural calculations manually or by softsware based on different Codes like ACI, BSI etc.

As thumb rule, it is estimated as below in normal case.

1) In Fotting  = 1 to 2 %

2) In Beam   = 1.5 to 2.5 %

3) In Column = 2 to 3 %

4) a) In Slab( Single Mesh) = 0.75 to 1.5%

    b) In slab (Double Mesh) = 1.5 to 3 %

This is only for quick and rough estimate. For accuracy, it need calculation and bar bending schedule.