How you chance 10mm steel bar to 8mm steel bar give formula?

Calculate cross sectional area of 10mm bar amd 8mm bar, then divide them and you will get the no. of bars.

For Eg. - Area of 10mm bar = 78.53 sq.mm

Area of 8mm bar = 50.26 sq.mm

No. of 8mm bars in replacement for 10mm bar = 1.562 bars [ theoritical]

In practical u'll provide 2-8mm bars.