Consider the respective diameters of the bar in the formula to get the weightage of the bar in kgs Just divide by 1000 to order in tonns the different dia of steel (dia wise)
I think you made a mistake when you calculate main bar & distribution bar i.e 6.5/0.15+1 = 44.33, 2.8/0.15+1 = 19.66, 2.8*19.66 = 55.05, 6.5*44.33 = 288.2 total = 343.25